Obviously, most sellers believe they are not sufficiently knowledgeable to make the sellling decisions on their own, and prefer to spend the extra 3% for help.

As of right now my credit score is around 720, would this be sufficient to get approved for a FHA loan?

However if you plan on buying 3-4units, there is a trigger rule for FHA, it is called the self sufficiency test.

And the second duplex hasn't appreciated sufficiently to take advantage of the capital gains exemption yet, so planning to hold for the next few years.For this third duplex, however, I would like guidance on how to title it:1) Given that I am paying cash, and I am not totally sure I will sell this within the "2 years in the last 5 years" rule, should I just put it in a LLC rather than my personal name (thereby missing out on the gains exemption)? 

In my opinion their data isn't significant for finding deals, but when it comes time to present an offer I don't know where you'd get sufficient data to do so other than CoStar.

Instead of focusing solely on typical tourist destinations, consider exploring areas surrounding National Parks, state parks, or unique outdoor recreation spots that lack sufficient lodging options, presenting a prime opportunity for short-term rentals (STRs).

There is no self sufficiency required. 

Quads on a septic system is going to be a major expense and you should expect to pump it out every 2 years or so, so it needs a man hole cover.If it is going to be septic be SURE you have sufficient soil quality for your drain field, you will want lots of sand.

Many investors find out too late that their deal doesn't cash flow sufficiently when using property management, and they themselves don't want to be active landlords. 

Might be worth simply waiting for current tenants to vacate.Also, in Washington you do have to provide 48 hour notice and if you can get a response to your request for the tour, that is sufficient.