Are there rules behind this type of investing? 

My rule of thumb is that the total deal profit (after closing costs, holding costs, rehab costs, everything) for the flipper should be 10% of the ARV .Shoot me a note if you find something - we're actively looking for flips in the SF & South Bay areas.

Following the 50% rule for expenses the NOI would be 31.2k.

The rules to Fannie/Freddie loans is that you have to loan in a person's name. 30 year fixed rates here with a lower rate than other loan types.

I've found the more restrictive you get the more likely you'll have for missing listings.

I have been using 70 to 75% as my rule of thumb yes. 

Have you ruled out conventional lending?

I know the rules are buying equal or greater for your replacement property and my replacement is worth 160K, more than my sale property of 100K, I’m just buying it for 90K.

There are some rules to know so do your research, talk to your CPA, etc. (2) pull out equity through a refinance.

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