A research fellowship is a temporary thing. It's typically 2-5 years, more often in the two year range.
It's effectively akin to doing graduate research, but instead of having a title like "research assistant" you get to act as a the research lead.
You aren't on the payroll of the university. You get a small grant package that pays for your living expenses and your research. If you were say at Princeton and doing your PhD in a STEM field, you would get around $90k a year. But the vast majority of that gets eaten up by your tuition. And you don't just do research. You are expected to go to conferences and get published. That all gets brutally expensive on a fixed income. Most of the prestigious and high grant money comes from private institutions, not government funding. And in my experience, I had to spend a lot of time getting private entities to fund my research. If you are on the government handout, you aren't getting enough to really do anything.
There is simply no way he could possibly afford a car or living on his own just on a research fellowship.
At least the typical graduate research student is getting their degree paid for. Since Will isn't getting a post graduate degree, I suspect his funding is around maybe $10k a year.
Someone in his state on disability would make close to $17k a year . Research fellowships are typically for rich kids that don't want to leave college yet and can afford to not have a job for years on end.
There is no fucking way his research grant is paying for his lifestyle. It has to be the bank of Mommy and Daddy.