One time I had to use my knowledge and testing practices after a job, and that was because it was a HUD inspired low income grant job for a homeowner.

Quote from @Jeff Roth:Monthly rents for mid-term rentals are about 20% (+/-) higher than unfurnished similar long-term rentals.I would not base the income potential for a MTR on a rule of thumb.

The two-family property now has better curb appeal and the rental units are much more desirable, which has helped me increase my rental income.

I am planning two ADU's at two separate properties, I'll trade a large yard for additional income all day long.

You mentioned W-2 income as part of a way to save on taxes. 

In your case, changing the property from a rental to your primary residence constitutes a change in use.The depreciation recapture will be calculated based on the fair market value of the building at the time of conversion, not including the land value.Since you're tearing down the existing structure, the entire amount of depreciation taken over the past two years will likely be recaptured, as the building's value at conversion will effectively be zero.The recaptured amount will be taxed as ordinary income, up to a maximum rate of 25% for residential rental property (Section 1250 property).

@Rory DarcyRecommend you first figure out the property Class you want to invest in, THEN figure out the corresponding location to invest in.Property Class will typically dictate the Class of tenant you get, which greatly IMPACTS rental income stability and property maintenance/damage by tenants.If you apply Class A assumptions to a Class B or C purchase, your expectations won’t be met and it may be a financial disaster.If you buy/renovate a property in Class D area to Class A standards, what quality of tenant will you get?

Freddie has a reno loan product that can be used for investment properties; this is only for first position, though.For the Heloc - it goes back to whether your mom wants to continue carrying the loan for income, and if so, how will you pay off the heloc once the rehab is complete?

Rental gives $500 monthly income from $2,000 rent.

-----------------------------------------------------------------------------------------------------------Recommend you first figure out the property Class you want to invest in, THEN figure out the corresponding location to invest in.Property Class will typically dictate the Class of tenant you get, which greatly IMPACTS rental income stability and property maintenance/damage by tenants.If you apply Class A assumptions to a Class B or C purchase, your expectations won’t be met and it may be a financial disaster.If you buy/renovate a property in Class D area to Class A standards, what quality of tenant will you get?