That's what house hacking is - getting roommates to pay as much of your mortgage payment as possible. 

-house hack or rent out your vacant units out to lower your monthly mortgage payment.

This is when you buy a primary residence (1 to 4 units, the more the better) which you can usually get for a very low down payment and get the best interest rates on and then rent out other units and/or bedrooms within your unit to pay for the mortgage and other expenses.

I put 20% down through my local bank on the first mortgage.

Inspection Costs - $400 Lender Fees - $1,000 Closing Costs - $2,000 Mortgage Payments - $2,500 Property Taxes - $600 Utilities - $1,000 Insurance - $200 Commissions - $4,000 Selling Closing Costs - $4,000 Home Warranty - $500 Termite Letter - $100 MLS Fees - $100 

Deduct NEW property taxes after you buyDeduct home insurance costsDeduct maintenance percentage, typically 10%Deduct vacancy+tenant nonperformance percentage(we recommend 5% for Class A, 10% Class B, 20% Class C, good luck with Class D)Deduct whatever dollar/percentage of cashflow you wantNow, what you have left over is the amount for debt service.Enter it into a mortgage calculator, with current interest rate for an investment property, to determine your maximum mortgage amount.Divide the mortgage amount by either 75% or 80%, depending on the required down payment percentage - this is your tentative price to offer.If the property needs repairs, you'll want to deduct 110%-120% of the estimated repairs from this amount.Be sure to also research the ARV and make sure it's 10-20% higher than your tentative purchase price.As long as the ARV checks out, this is the purchase price to offer.It is probably significantly below the asking price.

is that it typically comes with higher rates on the first mortgage, if you're low income enough you might qualify for near free DPA but most DPA's open to all income brackets are typically at higher than market interest rates.

BTC is the original but an infinite number of copies can be created, cheaper and safer.

With my mortgage eating half of my income, it sounds crazy to take a second one. 

Something to keep in mind though is that with the DSCR it is a new mortgage which entails higher closing costs as well as paying off any existing liens.