There also might be other legal/insurance considerations you want to factor in as others have pointed out.

Now depending on how this property was reported in the past, the agreement the two of you made, and possibly other factors this answer can change.

If you need an S-Crop depends on many factors: FICA wages/income and net profit.LLC doesn't save any taxes in BRRRRR.

I pay the bills and factor that in their monthly rent.

As others have pointed out, interest income from a partnership can be classified as either "portfolio income" or "ordinary business income," depending on factors such as the nature of the partnership’s activities, the number of loans, and whether the interest is incidental to your main business or a core activity.

I've included an example below to help illustrate this.So different lenders have different rates (which do vary even for DSCR loans) but these are factors they all consider.See example below:DSCR < 1Principal + Interest = $1,700Taxes = $350, Insurance = $100, Association Dues = $50Total PITIA = $2200Rent = $2000DSCR = Rent/PITIA = 2000/2200 = 0.91Since the DSCR is 0.91, we know the expenses are greater than the income of the property.DSCR >1Principal + Interest = $1,500Taxes = $250, Insurance = $100, Association Dues = $25Total PITIA = $1875 Rent = $2300DSCR = Rent/PITIA = 2300/1875 = 1.23If a purchase, you also generally need reserves / savings to show you have 3-6 month payments of PITIA (principal / interest (mortgage payment), property taxes and insurance and HOA (if applicable).

Factors like population growth, job market, rental demand, price-to-rent ratio, and local economy are crucial.

These questions might play a factor on price as well. 

(We're aware of the five year look back period for Medicaid eligibilty but it's not a big factor in our decision to do this.)We would get the house appraised so we can document paying FMV.House would be purchased with cash (it's a small home in a rural area and value is low)Inlaws would sign a lease so that it becomes a legitimate rental and we can deduct expenses, etc.

@Yi Chu,Another important factor you need to understand is that when an IRA is invested in leveraged real estate (most MF deals are), the portion of the income derived from the leveraged portion of the property will be subject to Unrelated Business Income Tax (or UBIT), which can be offset by using depreciation and other deductions.