If rates dropped 1-2% on a $600,000 home, it would cost a buyer $3,400 a month.

Majority of DSCR Lenders do not allow Manufactured homes but do allow for Modular. 

I turned the two smaller bathrooms in one of the apartments into larger one.

If so, you open yourself up to a larger pool of candidates.

(Property Meld for one)--- Owners often think a PMC can just enter a tenant's home to make repairs, but don't really understand the potential legal issues of entering when a tenant is not home.--- Owners don't understand the percentage of maintenance appointments tenants miss!

Would a home equity loan be a viable option in this situation, especially in regards to eliminating some of the red tape I'm running into with a refinancing an scorp-owned property?

Even introducing a moderate amount of debt and purchasing another, OR exchanging out of the existing into a larger higher yielding property type with some debt.

It does come down to DTI and what you can show versus what you can qualify for in terms of home price.

Consider single-family homes or small multi-units to learn the ropes.

It might make the most sense to just sell your primary residence and use it as 40% to 50% down payment on your future home.