I have about 30 years of construction management experience and I had a license in real estate brokerage  in Texas for about 30 years too. 

If you want to do anything beyond that list, pull the permit and keep it when you are done with construction.

I'm currently doing an intensive learning of RE Investing, property management and construction.

Before my bad medical problems that made me bedridden about 7 years ago, I was the proud owner of a flooring sales and installation business and was into construction management before the ownership for about 35 years.  

Whatever you do, be careful and invest in a growth area a diverse city and where you think we are in the real estate cycle. the age of the subject improvement and if there are any possible subject construction items that need to be covered up or removed by a special contractor.Good luck to you!

And I found out that most houses in Memphis are older like almost 20 years old houses and I'm kind of sceptical if it's worth buying old old houses, used to buy new construction houses.

For insurance it can depend on location, how old the house is, what the construction of the house is, if you plan on getting full rebuild or just enough coverage to cover the debt service.

  ( if it was not obvious the line had been replaced in the recent past or was not PVC.).Its one thing I see many turn key buyers miss in their home inspections is a sewer scope.. out in our market every realtor first thing they do is recommend a sewer scope I even have them do them on my new construction homes..  

An investor in your area that does new construction should give you some ideas. i would also Google it.

You're never too young to start :) my first deal was at 18, New construction flip of a quadraplex.