Also depending on how is home when you knock, their age etc....this could get creepy really fast. 

Replace them as they age out.  

Hey all, I have a general lease and clearly it is outdated with no mention of wifi or connected devices, wondering how you throw in connected/ wifi devices into your new age leases?

Instead of getting a general list, I would suggest you define some criteria, what you are looking for: for instance apt. classes (A, B, C, D), neighborhoods (A-->D as well), age of the properties, size (depending on interest and budget) you are willing to invest in.

Such a great way to start building a portfolio from a young age with as little as 3.5% down.

But with age and family obligations that has been a problem. 

And have them guess roughly the age of each and potentially if how much use each of them have left. 

At this age it becomes a time bomb that you have no clue when it will go.Like the other said. i also have seen 15 yr+ but i also replaced it as soon as i got the house.

You can only ask someone that invests in the same age/type properties in the same market as you.

I wish I was your age when I first started learning about RE investing!