Some of those being sales tactics, MLS access, network for investing, market data, insider industry partner networking, obviously extra income to supplement your USAF income, helping fellow vets/servicemembers and any buyers/sellers at that, and not having to pay an agent when you are accumulating properties as well. 

I have helped a few different clients build homes and then sell them or build to rent/keep them and it can be a really fun and exciting process if done correctly!

The reason I say that is because from the wording in your post, your still fairly early on in the process and may be susceptible to falling for the "next best thing" pitch that you'll find all too common both in BP as well as out of the forums. 

Also there's recent data that's showing there're more realtors outthere than number of home for sale.

We compile data on neighborhood rents and combine that with listing data, then double check rents, the area, and condition.

How long does it take them to complete the process?

We review a multitude of data sources to provide a real-time view into a real estate marketWhile a data-driven approach is useful to narrow down all the options, having boots on the ground (i.e. agent or contractor) is always important for due diligence

I'm not that professional but I think a whole house filter would filter particulates like dirt but not chlorine. for chlorine you might need a reverse osmosis system for a specific drinking water tap to eliminate the taste as it's not practical or efficient to put an RO on the whole house supply. if skin issues from bathing are a problem you might need a softener. sometimes when kids have eczema doctors actually prescribe "bleach baths" where a small amount of chlorine bleach is added to the bath water. also many of the water treatment systems can be rented so maybe just rent it while they are there. regardless, proceed with data. water test, pediatrician diagnosis (if it's legal to ask for, no clue), and a system that is right for the application. sounds like the tenant is willing to help out which is awesome.

I collected MTR comps and ran the numbers, and found that I might get an extra 15%-20% from a MTR, but I'm not sure if the vacancy rate I plugged in was reasonable (I'm in a mid-size city and my properties are close to Universities, hospitals, and other things that attract MTR tenants, so hopefully I'd have low vacancy...but I like to play it safe with my numbers, so I try to allow for a good bit of vacancy)... ...plus, all the comps I collected were just listings this month, and I don't know how much they're affected by seasonality, so my rent data might not be super accurate... ...maybe I'll give it a test run with one unit that's opening up in May, and see how it goes...

I would look at several funds to invest in so I can learn more about the process.