I would find out what is the going rate around your area. You don’t want to be too over the top. Depending where you live, some places charge 300 to 150, for a non refundable pet fee. Now you can ask for a rent deposit up to one month cost of rent to be held till they move out for damages and another months rent to be held and returned to them when their lease is up if they have not missed a payment. You need to find out what is legal in your state. Years ago places use to charge up to 3 months worth of rent. Two for deposit and the first month up front. I don’t know if that is still allowed.