You could say that, but when I worked with him I petitioned him to help increase my income and to direct more money my way in the most efficient ways possible, and over time that evolved into us working towards something bigger. I find Belial best to work with when you plan on expanding upon a business or rising in an organization - he’s a big picture guy, so while he can do what you’re asking it’d be best to keep an open mind with your request, rather than limiting yourself to 500 I would request a substantial increase in cash flow while developing your career further, so that the money gradually increases - this of course will require more work on your end.
A simple technique you can use to fulfill this desire, and still set your specified amount and/or timeframe if needed. That’s if you just want a simple and somewhat quick solution.
I’d sit down and think about it a bit, the other spirits may work just as well, if not better than Belial for your solution. From my experience quick cash just isn’t his thing, so looking into other spirits would put you in a better position if that’s what you’re after.
Edit: I think Bune would be the entity you’re looking for, after looking over what it is you’re looking to gain, and she might be a bit easier to work with than Belial as he tends to be a bit…intense, to say the least.