I would budget maybe 20-30k depending on how far you are going down.

Are there any pushbacks on this deal?  

Others have hit it on the head.

I've interviewed him twice on my podcast (once with @Chris Seveney and once on my current show), and I thoroughly enjoyed those conversationss. 

So advice to get the house against him and he will move out on his own is HIGHLY unlikely.  

There are numerous threads about sub to and many investors believe it is a high risk strategy (especially for seller) and believe buyers who use it “take advantage” of naive sellers.  

Check out other online guides available here: https://www.biggerpockets.com/guides3.

Do they have any reviews on Google?

You can use it as a downpayment on a property over $450k and use leverage tax free.

It's putting out lots of fires, managing finances like a hawk, keeping projects on time, in line and on budget, marketing the property & getting it through closing, and *then* doing it all over again - and that's if you're not doing any of the work yourself.