I have had to use my title insurance in 3 separate deals over the years.  

@Huiping S.Your mistake was to pull those together into one LLC; you should have kept them all separate and avoided several headaches that you would have to deal with from now on... 

Open up a separate bank account just for your rental activities.Have all your income and expenses run out of this account.This will make it easier to determine what is business.

Is it better to have both the parent and son on the lease and then have a separate guarantor agreement?

You would likely have to owner finance them in my experience to sell them separately. 

Anyway, my spouse and I have been separated for two years.

Apparently, Lester Bird had been instrumental in getting John Beck residence status in Antigua.  5 billion people and yet a small world.  6 degrees of separation!  

Just like you would do with any non-family contractor working for you:- get them to complete Form W9 for you, as you will need their SSNs- have them provide receipts for materials/supplies and keep those receipts- have a written labor agreement (how much and for what) - pay for materials separately from labor- make all payments electronically rather than cash so you can trace them- pay out of your business account, not personal- issue them 1099s next year if you paid them $600 or more for labor (for the whole year, not per job): https://www.biggerpockets.com/forums/51/topics/1167632-expla... 

Consider accepting the tenants if they pass your screen, deny the dog, require a certified clean bedbug report for their current home and belongings and a separate bedbug deposit to cover future treatment if needed.

They probably need to draft a separate document to assign that existing lease now.