First thing first, get qualified for financing and then think about floor plan, bathrooms, parking and the age of the home.

It seems that that age is right around when the effects of good/bad management begin to really show - some units are a little ragged, some pretty nice.What I want to learn is how to be precise about capex estimating.

Also is REI a good choice at a young age if I'd miss out on the compounding of the stock market?

First investment at age 19 paid me $80 every month through college.

At that age, even if they are spruced up, you'll want $75-125/month a unit in a separate repair budget.

At the spry young age of 22 I bought my triplex in Ohio in 2005 for $69k and no money down as an investment to pay for college. 

Regarding PITI funds, I would probably want more than 6 months earmarked depending on the condition and age of the property.  

We managed to pay off the loan by 2005.We bought our second rental in 2005, after taking out another equity loan on our primary, and again - - paid our "normal" mortgage payment, applied the rental from rental house number one towards the equity loan, made the normal equity loan payment and applied the monthly rent from rental number two towards the equity loan.In 2006, we bought yet another rental - using an equity loan on rental property two.That loan we threw the monthly rental money of the unit at.In 2008, we had paid off the note on rental number two and began throwing more money at the loan for rental three.In 2009, we bought rental number four and paid off the loan on rental number three later that year.In August of 2011, I retired from my job as a computer network engineer/database administrator at the age of 59 1/2, and began to withdraw money from my IRA & 401, using the losses on the rentals to offset the taxes on the IRA & 401 distributions.I had to use trial and error to guess how much to withdraw & be on the safe side as far as taxes go. $40K per year is roughly the "sweet spot" for that if you have 4 rental properties in the state of Ohio.

Im young myself but I hope people my age don't get the idea that it's okay to blow all your money at the club and not be able to pay rent.

The would give you an idea on the condition and age of the Boiler System for the baseboard heat.