I apologize sir,  I'm not trying to be difficult. I

One thing I have difficulty is estimating potential rehab cost estimation (as well as any big property issue that I should know of).

I am looking to purchase my second investment property and have done the other basic calculations that BP recommends, but am having difficulty in figuring out how to calculate the Cash on Cash return.

So I'll throw it out there, and if they decline then no skin off my nose!

And if they can to get their new property under contract before the sale closes.Sorry for your difficulties.  

Some precautions to consider:- Make sure the person who is the borrower of the underlying bank mortgage fully understands the implications  of a wrap, as well as the buyer- Consider a 5 or 10yr balloon note (vs. 30yr fixed) if you are worried that the seller may have 2nd thoughts down the road- Buyers should need to bring a significant down payment to the deal so that they have skin in the game- If your state allows a Deed of Trust for the wrap note, I suggest using that document (vs. a Mortgage) as it will put a lien on the house allow the Seller to pursue a non-judicial foreclosure if the buyer does not perform.- The home insurance after the sale (the new owner is the "insured") should retain the name of the previous owner(payor of the bank note) on the insurance as "additional insured" so as to not set off any alarms with the bank.- Use a 3rd party loan servicing company to collect all mortgage and escrow payments and make all appropriate payments to the bank lender as well as seller finance lender.   

They have more skin in the game then you do.Make sure you get clear title.

This is a real shame, because with the new pre-mixed urethane grouts like Fusion Pro, the difficulty of fixing an issue like this has turned into little more than a craft project.If she can find a tile guy who knows his stuff even moderately well, you're not going to do well with this in court.

The previous LL have zero skin in the game and will often be more reliable.

Now if you use a private lender then it is whatever you can negotiate and get them to agree to.Banks and even hard money lenders want you to have "Skin in the Game" In other words they want you to have some of your own money at risk so if things go bad you are less likely to walk away.