At his age, it’s not like he can start investing or manage a property, so I’m trying to figure out how to nurture this interest without overwhelming him. 

Then divide that cost by the amount of time between now and then and that's how much you should be putting aside for Capex.For general maintenance, the age and condition of the building will play into that.

So most investors just throw in the same expense factors no matter the age of the property.

It also serves as a great example of what I tell my college age daughters - email/text is a very hard place to have serious conversations without at least one person getting rubbed the wrong way by what can be inadvertent phrasing by the other party. 

Only "CASH OUT" of your IRA in cash of an emergency or you are at retirement age. 

show my age?)

All North DFW has the highest appreciation while South DFW will be giving you the better cash flow.If this is your first rodeo, then I would suggest to be close home if you are also planning to self-manage.Then the age of the properties and access to highways.

The house's age isn't so important as the age of the systems in the house.

Further, we need to account for a $10k “reserve” for what will be repairs / maintenance as the property ages.  

@Chris Seveney & @Jay Hinrichs Together you raised a good topic of discussion which is the new age Co-GP.