25/50c are the $50 NL tables or are you playing Limit?
If NL I would say 40x Buy In ($2000) for $50 tables full time as your roll is irreplaceable. That said if you wanted to 'take a shot' with the excess over $1000 once your roll hit $1200 then that would probably be OK, as you re still drawing out your daily income..
For limit they say 300BB I think which would be $300 but I'm guessing it's NL we are talking about.
You don't say how many tables you play at once or what sites you play at.
To increase income you want to be looking at 3-4 tabling and playing on sites like Tribeca for getting about 80% of your rake back as bonuses.
Good Luck
