I am now buying the House I initialy rented and I paid $400 Pet Deposit. The rental contract does not state, that the money is nonrefundable, so I am assuming I will get this money back. Am I right?

Not if there are additional cleaning expenses related to pet "accidents" or pet hair when you leave. Which are over and above any regular customary cleaning.

Never assume. Ask that this be indicated in the lease.

Not if there are additional cleaning expenses related to pet "accidents" or pet hair when you leave. Which are over and above any regular customary cleaning.

I am buying the House I am renting now... if there would be any problems, I would buy them too>
My Question was, if I can get that money back because I am buying!

Since you are buying the house, the landlord can't charge you for damages. I would advise the landlord now that you will be withholding the security deposits from the amounts paid over to him at closing. See if he raises a fuss.