If you have the cost segregation done by a reputable company then even if you get audited, you'll have proper support to back up your deductions.Now whether it's worth it - A cost segregation study can be extremely beneficial but its a case by case basis that depends on a multitude of factors.

If they’re just fishing and don’t need to sell, likely not worth your effort.

Having said that, typically the rents aren't up to market value and you could be inheriting bad tenants.

If you are in the City of Cincinnati, go to the historic conservation board and download some presentation packets for past projects like yours (worth the time it will take to go through them) and see which firms are doing them.Here is the site where you can look at other developers packets:https://www.cincinnati-oh.gov/planning/historic-conservation...

: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+, 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, 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.

How much does it typically cost for a SFH?

Home warranty's are not worth the paper they are written on.

: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+, 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, 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.

Surely the righ hike in rent will either make it worth your time to deal with the tenant or force them to reconsider moving! 

I've typically paid 50-60 depending on the size of the lawns.