I learned how to choose a good market to invest in (population growth, job growth/diversity, etc).

You can directly choose several small or big real estate projects to invest in.

As the Owner, you have the right to choose however you want to do it.

My biggest piece of advice is to CHOOSE YOUR MARKET WISELY.

Other landlords choose to buy in areas where the rents are consistent and high in relation to the cost of acquisition. 

I am torn choosing between a condo ($360k - $380k) or a quadriplex (>$950k).

Simply put, they are a viable means to getting home ownership within reach of those who choose this type of living.

All three areas are excellent, I would choose based on numbers for each specific house.

A big part of this is picking and choosing various unique colors/patterns/textures/and designs from different eras, and blending them together. 

If the lending route you choose to go decides they do require a certain net worth, you can always find a guarantor that will sign the dotted line on the lending that will, in essence, have them take on the responsibility of the loan in return for a fee or a percentage of equity in the investment.