Any developer with a website or public profile has probably received them: invitations to work on projects for "revenue share", where the developer is not paid up front, but instead promised some portion of the profits that a game may potentially make. Beginning developers might hear the promise of 25% or 50% share and start seeing dollar signs, but in fact they are unlikely to ever make any money off of the project. Here are the pitfalls of the "revenue share" position, and why clients shouldn't ask for them and developers shouldn't accept them.
Any individual or organization that asks you to work for revenue share, whether consciously or not, is trying to take advantage of you. They are asking you to work on their project for free, for the possibility of someday making some money if they actually finish their game and generate some profits. There are many reasons why you should not accept these offers:
Working for free, even for the promise of profit share, essentially says that your time has no value
Working for revenue share places all of the risk onto you. If the game is never released or does not make any money, you've wasted your time and gotten nothing in return. Meanwhile, the team that "hired" you got free labor.
Many indie/startup games are not profitable. Games built for "revenue share" are the most amateur and the least likely to ever get finished or generate any profits. Remember that 50% of $0 is still $0.
Even if the game does generate a profit, you might not get paid. It would be awfully easy for the person who "hired" you to "forget" to tell you their profits or to send you your share, in which case you'd have to take them to court to get what you're owed.
You might think "even if the game doesn't generate a lot of money, it will still be good experience/good to have on my resume" but even that is unlikely to be true. Here's why:
If the client wants to pay you in "revenue share", it likely means they do not have any actual money to spend on building their game. This likely means they are a startup with no experience, very bad at business, or (probably) both. If they don't have any money to spend on development, they probably don't have any money to spend on publishing or advertising, which means that even if they finish the game, they might not be able to release it or generate any publicity for it - dooming it to fail from the beginning.
When the client does not have any money to spend on professional developers, what they're probably going to end up with is a poorly-engineered project cobbled together by amateurs. You're unlikely to learn valuable new skills working on this project - instead, you'll probably be pouring sweat and tears into an ugly and buggy mess that you'd never want to put in your resume even if the game actually gets finished.
The client is likely to have the least skills of all - after all, if they knew what they were doing, they wouldn't need to convince you to work for them for free. Often times, the people pushing these projects are very young and very inexperienced - they are the last ones who should be trying to manage development of a game. You'll hate working for them. Worse, if the game doesn't get finished, they'll probably stick some screenshots into their portfolio without ever mentioning you or your contributions, and then try to use your hardwork to land themselves a paying job.
If you want a good way to develop your portfolio or network yourself and aren't concerned about getting paid, there are other options:
Work on your own games! Start out small, and build from there. If you are a beginner, it can help to start with a game template from the Asset Store, which also provides you a lot of code to learn from - but choose very carefully, because many templates are created by overseas developers with terrible programming skills. Do your research and try to pick a template developed in an English-speaking country with reviews that mention quality code!
Work on mods for popular PC games. There are a lot of modders out there, and modding work alone is not going to give you a rock-star portfolio, but it still helps to build experience and make connections with other developers. You can learn a lot more from building mods for a professionally-developed title than you ever will working on amateur games for revenue share.
You think you've got a clever idea for a game, and a clever way to take the shortcut to success. All you have to do is find some motivated young developers willing to work for profit share, and soon you'll be raking in the big bucks - right? Think again. Here are the flaws with your plan:
Professional developers don't work for free. Anyone with any kind of industry experience is going to reject your "revenue share" invitation immediately - in fact, they'll probably consider it insulting. The only developers who will consider your offer are young hobbyists - often people in their teens or early twenties, entirely self-taught from Unity tutorial videos. They do not have the background education or professional experience to build a quality game. They may have terrible coding practices, poor organizational skills, and a limited grasp of the engine. They'll often use the wrong tool for the job, add more bugs than features, and rack up the technical debt.
Even if, by some miracle, the game gets finished enough to throw it onto Steam or Google Play, you'll probably get slammed with 1-star reviews. Nothing looks worse for the reputation of your company (or yourself) than a buggy game with poor reviews, particularly when the developers who worked on it start posting on forums that you never actually paid them anything.
Running a studio is not as simple as "build game, make money". You have to set up distribution channels for your game - at the minimum, this means paying to release the game on app markets like the Apple App Store ($99/year), Google Play ($25 one-time fee), or Steam ($100 / game). You have to set up advertising; hundreds of new games get published every day, and posting about your game on your Facebook wall is not going to bring you any downloads. Effective marketing campaigns can be expensive - plan to spend hundreds or thousands of dollars on marketing (if your game every gets finished at all). You also have to support the game after release. This means responding to customer emails, tracking down issues, fixing bugs, and sometimes buying new hardware to test on. Have fun trying to fix "the game doesn't work right on my Galaxy Note S9" if you don't even own a Galaxy Note S9.
Your ideas are not new and you've got too much competition. As a freelancer, I receive hundreds of project invitations each year asking me to work for revenue share. These are often from clients who think they are extraordinarily clever and have an idea that will generate millions - but is actually generic and highly derivative. With all of these start-ups trying to solicit free development work, why is your project going to be more successful than anyone else's?