They are mocking these up with interest only loans and factoring back in the tax deduction as if you qualified for the tax benefits of a real estate professional and factoring in the diminished first year property tax (since its not a full year).

For a rule of thumb, replacing a commercial boiler can range anywhere from $20k to $150k, depending on the size, age, and efficiency.

If scaling quickly is your goal, DSCR loans are a great tool for the refi portion since there’s no 12 month seasoning requirement like conventional loans, and DTI isn’t a factor. 

That is $19,200 annual profit so you would be -$3,200 in 1 year with no factoring of breakage and maintenance.

I'm running your numbers and getting in the low 20% range.

Is it fairly priced for the size, location, quality, and other factors?

Determine what type of property you want to buy - What Zip code, what condition homes, price range, etc.Contact 3-4 realtors that helped buyer agent buy the type of homes you are looking to buy.Then go with the 1 realtor that you connected with the most.

It's been great - the property is 100% paid off and the house is worth 300-340k generating approx $2300/mo (that's after utilities/management fees etc.)I'm considering selling the property to buy 3 more within the same price range in the same market. 

Quote from @Jaycee Greene: Assuming you pay asking price, I'd estimate the down payment for something like that using a hard money loan (HML) would be around 40% of the purchase price and your monthly payment would be $2,600 with an interest rate in the low 7% range (probably need a 700+ credit score to get that).

I have a lengthy Legal Opinion, from my seasoned Legal Team regarding this matter.There are several important factors, when thinking about proposing Seller Financing.