I have great renters who try to follow all the crazy rules that the hoa has made up.

“Joint User” Rule.

And the one i live in.Under the current fannie mae rules.

As mentioned above...airports can be a costly venture and they can be quite complicated due to FAA rules - BUT LOTS OF FUN :)   There is a ton of information out there though to help you.   

To meet this objective I use the 70% rule to determine my All-in costs Target.  

I have great renters who try to follow all the crazy rules that the hoa has made up.

A general rule of thumb is 90 days at 90% occupied, but again, I would hold on to the seller finance as long as possible.If you are buying out the seller completely when you do eventually refi, yes, you will need to have some equity (whether that's your own, or another private investor / partner). 

I didn't know if it was some hard and fast rule that I hadn't heard of before.

I have posted a few times and I will admit that I have not read all the rules so I am going to post carefully.... hand one "flagged" in the past but no understanding as to why.I have been investing in RE for many years in a passive nature but just sold a couple of homes that were deprecated out and made some good money and thought.... if I had only had done that x 10 I would be set.I recently attended a $250 3 day event after attending a free 3 hour event. 

I follow exactly the rules that @Brandon Turner suggests which is the %70 rule or even %75 rule which is: Buying at %70 of the ARV - rehab costs.