There's a way around that. Bloo, feeling unappreciated, decides to cook dinner for the house so he can bask in all the "thank you's". The residents get divided up between a few hundred temporary homes for a week or two while the biohazard crew cleans up after him. Frankie, being temporarily out of work, tries out various jobs and can't stand any of them for more than a day.
The episode ends with Cheese wandering around the kitchen, saying "I like toxic waste".
Seriously, though, one does wonder what Frankie would be doing if Foster's closed down for whatever reason (hopefully because everyone finally got adopted), or if it had never opened at all. Nursing is my guess, or perhaps social work.