Single family, 2-4 unit? 

Our options are to put the money the stock market, buy a multi-unit property, by an established business, payoff the 3 rentals for cash flow, or get into hard money lending.

I’ve got 31 units, and I’m sure there’s 4-5 other landlords with 15-50 units in my area.

I have the opportunity to manage someone else’s 10 unit commercial building.

It shows how many searches have been in the past 12 months for a city and gives the price range of units in the area.If you choose to contact a hospital ask for HR or if they have someone who specifically works with traveling nurse placement. 

 Which city in the United States has appreciated the most over the past 10 years?

There's no difference in a local flipping a house than flipping the small mixed-use building that is vacant in town into a couple commercial units and some apartments above. 

I am new to the world of real estate investing and want to one day own properties and rent units out.

Quote from @Gregory Wilson:As for the second, there are only about 20 monetary numbers to be entered in Turbo Tax on a single unit rental property 1065 so it always seems to me that the $3500 would be better spent elsewhere.

I think it is different if you live there, speak the language, know the market.