Have rewired or done extensive electrical work on almost all rehabs as well.

I travel extensively for work and have been outside the US for extended periods (4-12 months) on multiple occasions.  

@Graham Melvin I've written extensively on the subject.

If you do extensive research or just know the market, you'll see 4-plex buildings that were rehabbed AND I've seen the rent rolls double.

In the end, all of this was time consuming and we ended up taking the house to the wire – even with a 15 day extension.  

If you are worried they may leave ask them to sign a 2 year extension and you'll put in the door.

I'm looking a a home  for a flip which needs fairly extensive work but it looks to be manageable.The house was listed as built on a slab but when I looked it turns out there is a crawl space and a cinder block foundation -house was built around 1955. 

This is a great extension of what you already do - Great choice.  

On extensive remodels we have come in way under that number.  

I have been doing extensive networking, and am very excited to meet so many intelligent and interesting people.