I've already put down a significant deposit and now I'm considering leveraging a 100% loan for a second property, with a budget of up to $600k.

I do think you can normally get funding in that time frame and it doesn't have to be actual cash for balance but I do think the deposit has to be cash, debit, certified check etc. 

They and their competitors guarantee the security deposit and the rent for a monthly fee.

Sounds like property taxes were up to date… what state did you buy this in.. some states like Ohio sales work this way you put up a deposit of 5 to 10k sometime a tad more then you have a settlement when the judge signs off.Or maybe this is a private auction and you just put up non refundable EM maybe ??   

If you transfer money into it (particularly large deposits for down payments), they would just want to show that trail and where it came from. 

The vast majority of lawsuits against Landlords are for wrongful eviction, security deposit disputes, and Fair Housing Violations.

You will just need a signed lease and possibly a security deposit/first month's rent prior to closing on the refinance since the appraisal will mark the property as vacant. 

Withhold the amount from their security deposit if allowed.6.

Your enforcement remedies under law are: 1) deliver a notice to pay per F.S. 83.56(3), 2) make a claim on the security deposit when they vacate per F.S. 83.49, and 3) seek collection of unpaid rent through lawsuit or collection company. 

The lease agreement clearly states that the "Security Deposit", and not "Damage Deposit", does not have to be returned to the tenant if all the terms of the agreement are not met.