I believe you can charge up to 300 per pet (deposit) and up to 35 / month.

Obtaining Non-refundable deposits.

Now, I'm imaging a scenario when every one of these tenants move out that I'll be paying their entire security deposit + interest even if there are damages beyond normal wear and tear. 

This one I might take from the deposit, depends on how much if it is really worth it.

Please consider this if you move forward.Additionally, you need to have a broker on payroll in illinois and three separate bank accounts with the security deposit trust account located in illinois.

Certainly one account for each LLC, (separate for security deposits based on your local rules)

Would it be a good idea to take a deposit to secure the deal until the rule clears?

Furthermore if they are always paying they probably will stiff you in the end if they know they aren't going to get the deposit back. 

You can't beat the price, either, or the interest rate on deposits.

This method is simple, free, and fast.You could also provide deposit slips, so tenants can deliver their payment directly to the bank.