If they sell below the determined FMV at the time (likely) to my understanding they can claim capital loss which can be spread over years at $3000/yr.

I've tried the premixed thinset mortar but it is hard to spread and requires dry/cure time of approximately 48-72 hours for larger tile, such as the one I'm using.

That could be spread on top of the remaining 18 months of payments or simply balloon at the end.  

A few points about sandwiches:Get a good spread in the rentGet a good spread in the optionGet a spread in the back end between sales pricesSplit closing costs on AB and BC closingsConsider doing a reverse assignment on your profit by assigning or selling your interest to the seller, use a second note, create a new lease option between seller and tenant buyer so you have 1 closing.Have 3 to 6 months reserves in case of evictions and damage and marketing expenses for new tenant.Get the tenant buyer into a good mortgage origination coach immediately so you can have a closing. :)Account Closed

So from there, consider the spread in the amount of time you've spent researching your properties and the long term wealth potential that a property will provide based on that benchmark.

This is done if there's a spread in the rents that's worth the risk.The assignment gets you out of the deal.  

One of the opportunities we are evaluating at the moment has five buildings (18 units) on one ~3acre lot - financing would be a commercial mortgage covering the entire site.Other times you may wish to have a blanket or portfolio mortgage spread over several properties - though up here (Canada) they are difficult to arrange these days (I do not think any lenders are going to offer them on residential properties).The biggest advantage (IMHO) of a blanket or portfolio mortgage is that you have the equity of several properties securing the note.  

Some people will say that $100k is a big enough spread to make money on...but that may not always be the case (I don't know the Houston market, but here in NJ some houses in nicer areas could have property taxes of $15-20k per year or more, this makes holding costs add up really fast). 

If so there are opportunities for some huge spreads in the area.When I talk to my realtor they seem to think a lot of the potential will be based on business development in the area.

The larger firms often calculate with a VAR model to produce the credit spread acceptable for their transactions.I hope this helps!