Hopefully this helps clear up the main point of your post!

Staging your house well can help you attract more attention from buyers, which ultimately helps it sell faster and maybe for a higher price than an unstaged home (see visual):What Are My Staging Options?

Tenant occupied properties can be attractive to investors if cash flowing...no one wants to buy someone else's problem. 

Yes, its mainly ordinary income from interest payments.

.)- Average days on market- Absorption rate- Historical data on rents and sale prices in the area- Population growth- Main economic drivers (industries, individual companies, etc.)- Crime stats... if you know specific zip codes/submarkets that you'd like to target, the best data will come from local precincts. - and more..I'd recommend remaining active not only here on BiggerPockets, but in other valuable RE investment networks that you can find - i.e. local meetups (meetup.com, eventbrite, BP local events). 

My main goal is it be able to retire at age 40 from my main job and work entirely on my real estate portfolio.

Main thing to watch out is DSCR Ratio.

@Jack Cottrell You Vacancy & Maintenance percentage are aggressive and may only work for a Class A rental/tenant.If the is a Class B or C rental that will attract Class B or C tenants, you should strongly consider increasing those percentages.NOTE: we deal with a LOT of Class B & C rentals, so we replace "Vacancy" with "Vacancy/Tenant Nonperformance".

I currently own and self-manage two STRs in Maine and should be closing on a small 'cabin campground' with 10 cabins nearby that will also be operated as STRs. 

Although as @Drew Sygit asks, what have those PMs that pledged to do it better now learned that may bring them back into line with main stream service providers?