Agree with Michael S. that knowledge is power and it will help to build your confidence the more you read and absorb the material on this site.Check out all the podcasts, I listen to them in my car during my daily commute.  

Hope you got real and current cost estimates from licensed contractors and made sure the stated , thought of or planned materials are definitely available at quoted prices so you do not get caught off guard.

It all depends on the quality of materials and amenities you will include, the size of the unit, ceiling height etc.

What are some of your favorite personal/ business development books or any other learning material that you feel has helped you out a lot?

I will stop by Home Depot tomorrow and calculate how much all the materials will cost me. 

Paint is $1/sqft inside outside $1.25-$1.50..again all depends on the local market the type of material etc. 2.

The most important thing at our age is to sponge in as much learning material and experience as possible.

Initially we were going to get a separate one for each, but then a well-known real estate investment guru my wife has ghost-written some material for suggested we should put them into a single LLC holding all four properties in separate land trusts.

Different roofing materials - like HVAC units in some cases can have a different life expectancy.  

We did get some estimates and because of the special way they have to remove it and dispose of the materials it was costly.