If you're offering amenities and similar quality/or better then you should be able to receive many candidates to choose from. 

They said they needed to talk to their supervisor and then called back and left a voicemail but I haven’t called them back yet.

If the answer is yes, then the next question is what market do you want to invest in?

If my verbal offer is entertained, then I would contact my agent to have her set up a showing and make a formal offer.Is this reasonable?

We signed the contract and then they were always late on the payments.

In this method, the buyer makes regular payments to the seller over a set period and then makes a large final payment (balloon payment) to complete the purchase 

She buys them distressed, renovates them, and then sells them herself for top dollar. 

The goal is to buy a whole note at a high discounted yield, then recapitalize by selling the whole note or a partial at a lower yield or borrowing against the note at a lower yield. 

This is what I would tell them.If the offending tenant was warned by police or cited by them as verified by a police report then I talk to them about it and follow up with a written lease violation warning aka notice to correct.

My best advice is buying a rental that will cash flow as BOTH a long-term rental and then seeing if it will work for a MTR/STR afterwards.Aside from that, STR/MTR will take a lot of time and resources.