If you are ok with covering the existing flooring, you can use foam or sponge underlayment and then cover that with carpet or other flooring material on top of that.

All 3/2's?  Have

To sum it up, building right now is an uphill and costly venture with narrowing margins for the builder and extremely high purchase prices for newer energy-efficient construction.Great time to invest in the manufacturers of spray foam insulation, solar batteries, and start thinking about adding car charging ports to your existing MF properties if you can.

You can shop around different title companies, but that shouldn't shave off more than 1k-2k. 

They could live in one unit and use the income from the other unit(s). Have

. - Install anti freeze wrap on the pipes and cover in foam wrap.

If outside you have choices from rigid foam to spray and others..you don't want a thermal bridge....Here's a good read on that. https://www.ecohome.net/guides...

I also know they are in their 50's, have their own electrician business, and they bought the house for 25k 3 yrs ago.

I you need the money to make the next deal "go", 1031's have their place.  

I travel for work and have been able to maintain some type of loyalty with the airlines which can help get some time shaved off should I need to check bags.