how to deal with pests issues in a cost effective manner, tired

We are have a portfolio of about 40 properties and pests are always problems for us.

I am tired of keep calling pest control company since they are all kinda expensive.

Now, one tenant just moved out and left lots of fleas from their little dogs and when I came in I got bitten all over.

Any good solutions out there for fleas?

Also what do you do with roaches? I used bombs before but they keep coming back and I ended up calling the pest company after too many complaints.