One of the challenges I can already see is understanding permitting and zoning restrictions for STRs depending on the market. 

Maybe I'm just the odd man out here, but I don't want any of the booking sites providing any access information to my property before the guest's 4 PM check in time.

Another thing I would double check is the zoning and/or any restrictions that may effect the lot as some don't allow manufactured homes.

The main restriction on using the Section 121 exclusion is the ownership and use test.

Are there STR restrictions in those areas ?

You're basically playing the odds.

I've personally transacted on a house +ADU + JADU that was rented to three separate tenants.If I am taking the risk of breaking a deed restriction, I expect the associated discount. 

Do you know of any in Scottsdale without minimum rental restrictions?

After 3 or 4 years of the county fighting our neighbor, they passed a very restrictive ordinance that affected both the neighbors property AND our property.  

Populations in the 300-500K range are generally a good sweet spot.Roll multiple smaller cities/towns up into one larger “target market” if you need to Reasonable Property PricesStaying at or slightly below median market value increases your odds of success since there are more buyers/sellersHigher price points can be very lucrative but typically require more time/money for marketingGrowing or Stable EconomyTarget market should have positive economic growth expectations.