Use other online RE websites for more accurate estimates.Second, you just earned 40K s in 1.5 years ... what will it be in 10, 20, 30 years? 

I just filled two vacant rooms in a group house in Petworth-- I use craigslist, zillow, zumper (although the leads through that website are questionable), and Facebook DC room for rent groups. 

In my 5 or 6 years of access to this website on a full time basis, I have never heard that the interest rate matters on any deal, just know what you'll be paying when you do an evaluation or figure the worst case scenario. 

It also lets you have a white listed portal on your own property management website I believe where you can use your own logo so that your clients see that you're investing in the tenant experience. 

I just came across this website with a nice graphic that may help answer:https://rentalhousingjournal.com/legislation-changing-in-many-states-to-make-them-less-landlord-friendly/#prettyPhoto

What’s the difference between the free ultimate beginners guide on the website (53 pages) and the book on Amazon (287 pages)?

On the HUD website there are two lists: one for all of the FHA approved lender in your state who are servicers and originators.

You can search for that here on the site and Zillow has info on their website on both topics as well.

What website or websites are best to us to crunch numbers to get your ARV price and find your low and high comparable properties?

It would make sense to me that if a person wasn't doing their investing through a business entity that it could affect their DTI and thus their ability to take on more debt.Even if your projected rental income is included in the calculation it seems unlikely to me that you'd be able to find a property that cashflows enough to not affect your DTI.I guess to provide a more specific example say your current DTI is 25% ($2000/month with $500 in debt).If you were to buy a house that rents for a $1000/month and the mortgage payment is only $750, that brings your monthly income up to 3000/month and your monthly debt to 1250 so your DTI would jump to ~42%.Obviously that is a drastic example because that is not much income to start so the change is more drastic than I imagine would be for most on this website, but still the change is still there.