The fha 100 mile rule will be triggered whenever you try to vacate your current primary and also trying to use the rental income to qualify.However, this 100 mile rule can be exempted for the following rulesRelocationIncrease in family sizeVacating a joint owned propertyNon-occupying co-borrowerIf you are not trying to use FHA on your 2nd househack, you can use conventional and the rules that I mentioned above will not be a concern.

All these comments about Tax, and Managing property,  is the reason we operate as an I.R.S. designated 501 (C ) 3 Tax exempt non profit association of landlords.  

I’d appreciate any financing/partnership feed back.Buy a cheap flat, fix it up while living in it, sell & take the 250k exemption, rinse n repeat.

Dodd Frank will apply...see below.Not More Than 3 Properties Exemption Any person or entity cannot provide seller financing to an owner occupant more than 3 times in a 12 month period without using a MLO (mortgage loan originator).

More and more states are requiring a form exempting from collecting % as a withholding. 

Since I’m buying a new primary home, would I lose that tax exemption?

This is not a problem if you use a licensed CA real estate broker to originate your loan since they get an exemption against usury for loans secured by real estate.My strong suggestion is to find an experienced hard money lender at a local real estate club to originate the loan for your lender.

I believe Airbnb's policy said hotel's were exempt.  

Most purposes that people on the BP forums are transferring properties to an LLC, would be exempt of the Due On Sale Clause. 

The typical 506 structure is an EXEMPTION from the SEC, so there is no set capital requirement for doing so, since it allows you to raise money publicly (depending on the structure) without having a securities license.