This is pretty clean.Scenario 2:  Your partner has owned the house for 15 years and has been taking accelerated depreciation, so the book value of the house is very low. 

that we’ve learned in our 24 years, managing almost 700 doors across the Metro Detroit area, including almost 100 S8 leases:Class A Properties:Cashflow vs Appreciation: Typically, 3-5 years for positive cashflow, but you get highest relative rent & value appreciation.Vacancy Est: Historically 10%, 5% the more recent norm.Tenant Pool: Majority will have FICO scores of 680+ (roughly 5% probability of default), zero evictions in last 7 years.Class B Properties:Cashflow vs Appreciation: Typically, decent amount of relative rent & value appreciation.Vacancy Est: Historically 10%, 5% should be applied only if proper research done to support.Tenant Pool: Majority will have FICO scores of 620-680 (around 10% probability of default), some blemishes, but should have no evictions in last 5 yearsClass C Properties:Cashflow vs Appreciation: Typically, high cashflow and at the lower end of relative rent & value appreciation.

I'm eager to learn more about:Identifying undervalued properties: Are there any specific strategies or resources you recommend for finding deals below market value?

Building an ADU is a nice way to add value but you won't get that funded by a lender. 

($390 value)”...

basically if anyone has any tips when it comes to researching plots of land in order to make the right purchase i would greatly appreciate it get with a realtor. we underwrite land at no more than 10% of after built value. in our market we build under the average new build value which is about 515k. we like to be around 420-450k and smaller footprint about 1500 sq ft with attached garages. we build close to urban core where everyone wants to live and net migrations match up. but suburban is fine. if you give more context I can help but in most markets land is a buyers market. most people aren't looking at it or buying it. 

I was looking at an attractive rental but it looks like the land value is 75+% of the value, so I would be paying a ton get very little tax benefit. 

When they started screwing with us last week about appraisals and then having to give them an ‘after reno’ price for the house when they had no idea what we were doing the house to increase its value, I did mention to the partners I thought we’d been scammed.

Part of this is sentimental value (wife's grand father built the house) but I don't want it to be a money loser. 

Don’t do it, be firm, but still find a way to show tenants you value them.