Understanding the value of your own time.

AKA - how much should I ask for doing XYZ?

First thing I want to say: If youre good at something, never do it for free -If you do it for free, youre an exploitable idiot, and youre not only hurting yourself, but the industry itself. Im not talking about free modding or community projects - I'm talking about getting exploited for "exposure" or "future business ventures", "royalties" etc. Just don't,.

There are two ways I can answer that, short and long.

Short answer:

TIME YOU SPENT DOING THE WORK x HOW MUCH YOU CHARGE PER HOUR

(Client dont always need to know how long it'll take you, sometimes they dont care - it all depends on the job really, but you should always know these two values - how long and how much)

Thats it, easy. However, it works when you remotely know how expensive life is, but if you've been linked this post, most of you probably don't, or don't know what to include in expenses when freelancing, so here comes the long answer:

TIME SPENT DOING THE WORK x (Hourly rate + financial buffor + equipment cost/wear buffor + software + power cost/internet cost + taxes + additional factors)

Let me describe what means what:

Time spent doing the work - you need to know how long you'll work on the asset - 5 hours? 50 hours? If you agree to make a gun model, because OH WOW ITS REMOTE WORK I LOVE DOIN 3D AND SOMEONE WILL PAY FOR IT! - I understand, its cool, we've been there. However, if you agree to make a gun model for 200usd, and it'll take you 80 hours (and remember there might be additional feedback / issues at the end, more about it later), Its suddenly 200usd divided by 80 hours of your time, which equals to nice... 2,5 USD per hour. Depending where you live, you might get more working at McDonalds, so the choice is yours. This is the reasons you see professionals charging up people for thousands of dollars for one AAA model - not because they're assholes, but because work takes time, and time is everything. You have 24hours in a day, I have 24hours in a day, so does the client.

 Hourly rate - hardest thing to estimate here, because it depends on how niche the thing youre doing is, how large is the competition in area youre working now, and how much people of your skill level are out there. It is not rare to see Juniors working for 15usd/h remotely, middle artists for 15-30usd/h, and seniors for 30+ (Personally I know people who charge 120usd per hour of their time - it seems a lot, but like with everything - there is a catch). This is the value you'd want to earn working in a studio, or on-site work.

Financial buffor - this is where extra stuff starts. Ok, you have a self-employment company, or just remote working for some client on a contract-based work (it strongly depends on the country you work IN and FOR, its your responsibility to check all the formalities) - if you're lucky, you have constant flow of work, 40,50,60hours per week, paid on hourly basis - and thats great. However, there is always possiblity, that the work will go dry, there will be one month pause between projects - what then? Exactly, your financial buffor. Depending how expensive your area is, its good to have SOME savings, for me its usually calculated in a way that for working 3 months, I can live 1 month without work (so spending 3 hours of work, you charge like for 4 hours). And try to save up this money, don't spent it on videogames,whores or whisky. At least try not to. 

Equipment cost/wear - if you're young, and do work on a computer you have from the college times, and always had one, then its probably weird for you, but if your source income is actual freelancing/contract work, its VERY IMPORTANT to be able to do the work. The more complex work you do, the more powerfull machine you need. Now imagine you just got a contract with 2 week deadline for a model, and on second day your PC dies. You waste time for debugging what happened, waste time for looking for parts, waste time waiting for parts to arrive, wasting time recovering the work you had opened (you have backups in case harddrive fails, right? :-) ). And  thats if you have money for new hardware. If you don't, youre screwed - sometimes a cheap laptop CAN DO JUST ENOUGH, but with more complex tasks, its mandatory to have a higher perfomance hardware. After 15 years in the field, I have ready-to-use secondary workstation that have almost identical parameters as my main one, + few server rackable computers with backups / rendering possibilities. In big corporate world its called hardware resource scaling, and after some time, its good to have money to do it as well.

Software - if you pirate your software, we wont be friends. And youre probably limiting yourself to clients who pay less than a fast-food joint, so its your loss as well. Software costs a lot. Now its hidden under "subscription" pricing model, but after a year or two, you start losing money on it. Its just 100usd monthly, but normal licence cost 3000 usd, so after 3 years, youre paying extra. But have updates, thats a trade-off. Most of my game-dev work CAN and IS done on... 3d Studio max 2012. Why? Because I have lifetime licence for it, costed me around 2000USD. Its 2020, and 3ds max cost 300usd/mo in my country, co after 7 months, i'd start paying extra, for rest of the 8 years. HOWEVER - I'm drifting off here, just wanted to show the alternatives - software (unless blender) costs as well, and if you work on game models, you probably want at least 3d modelling package + texturing package. So keep it in mind that you need to incorporate the cost into hour price as well (assuming you work 200h/monthly, you can add 2usd to hourly rate, and you'll have 400usd for software - not counting initial windows licence cost, it should be enough for monthly subscriptions + a plugin or two monthly.

Power cost/internet cost - Thats the funny one, because its often ignored. Unless you work just on models and textures, on a laptop (You should get workstation though), it won't affect you much. However, if you do renders / simulations / CUDA calculations, it might affect your monthly bills a lot - I had contract where I had to render multiple versions of lightmaps for unity game, and it turned out in 20 days I've used 1200% more energy that I've used previous month in total. And I needed to pay for every kilowatt spent anyway. With internet it really depends on the work you do - if you work on movies/raws, there is a lot of data to be transferred SOMEWHERE, and you don't want to miss deadlines, because you had 60kbps transfer to clients server - thats why a good connection (not only in download speeds, but upload speeds) is a must. Or two of them. I have 1 connection to my home + one backup LTE router if it fails, but I plan on getting second wired one, as projects sometimes hits 100GBs of data that need to be transferred.

Taxes - welcome to the adult world. Everything you earn, is taxed. Depending on your country, it can be 9,5%, it can be 22%, it can be 39% - we wont discuss how fair or not it is, but you better pay these taxes, or IRS (or local equivalent of it) at some point will make your life hell. Dont worry, clients (if its a company, not some backward savage garage-based venture) know that, and if they don't employ you on normal contract, but outsource work, don't pay the expenses, and should be ready for you charging more than on-site normal employment. If freelancing is your way of living, I strongly suggest hiring an accountant as I do, to take care about all the taxation purgatory.

Which brings me to last point:

 Additional factors - just like that accountant I've mentioned before, there is a lot of things related to your work, that cost money. Im not talking about rent or food, but things like office costs, cabs, alcohol, website domain/server if you have business website, some small marketing even. New plugins, tutorials, resources - if you can pay 5 dollars for a pack of decals you'd spent 4 days making, just buy the decals. It'll depend strongly on where you are at the career path.