I would be willing to drive out as far as Butte (some nice neighborhoods in Butte are very comparable to some multi-families in Great Falls) to do a showing for you. 

I just want to confirm when using the 50% rule, we only use it to compare to the mortgage amount and not taxes, insurance, etc.?

The purpose of doing that is to verify that what's been recorded is up to date.

Any suggestions on best way to find what the rent is in that particular area and compare to the homes I find on Zillow?

I try purchasing only things that are either multi-purpose or can be folded or collapsed. 2.

i would stay away from SFH as your first purchase. you are 100% responsible for that mortgage should something happen like you lose your job or something. a multi family gives you breathing room. one thing to keep in mind is the taxes...sure the Bronx may have higher prices compared to NJ....but you can find properties in the bronx with 2-3k annual property tax rates.....while Jersey has some of the highest property tax rates in the country. factor that into your math and not just the purchase price. 

not a great deal compared to buying 5 year term first trust deeps on performing rentals that pay 9 and 10% and you get paid off in 6 months then what .. no return.. until you find another deal so your drag on money turns your return much lower.. now if it was 10% or 7k over 6 months that would be something to think about.. but not an interest rate for such a short duration.

They will also loan on properties that require a lot of work, which gives you the advantage compared to a conventional bank or a FHA loan. 

How does that compare to the market?

Comparable homes in the area have sold this year for $600,000 plus ($40,000 appreciation in just 1 year).