Plan for 15 to 25 percent of the electrical budget to be discovered work.Biggest early mistake I made was not getting a structural engineer involved before closing.

It cost about $2500 to replace the water heater.

Hopefully no slab leaks, hvac replacement, roof replacement, window replacement, foundation repairs, hardscape repairs/replacement, etc in the first 3 years.How did you derive your 10% maintenance/cap ex (5% each) estimate when you did your initial underwriting?

Engineered cost segregation studies usually start around $3,000 for SFHs and go up from there depending on the property. 

But warped floors in a 1998 house means something is wrong (at that age, it's likely under-engineered framing).

I'd recommend detailed engineering. 

They might need to hire an engineer to confirm their DIY study.

So, start from there and do the reverse engineering.

Now to be fair the company we are funding is a Civil engineering firm with deep experience..

The estimated tax savings that these cost segregation companies provide are normally invalid as they don't know your whole picture.For example, the tax savings of $68,000 is laughable.Your income of about $100,000 is likely going to be taxed somewhere in the 22% tax bracket(Unsure of your tax filing status).Which would mean, even if you can take 100% of the losses, that your savings would be around $22,000.There are two different types of cost segregation studies - Studies where Engineers are stopping by the property and creating a report for you - Starts at $2,500Studies based on completing a questionnaire - Starts at $450I normally recommend one study over another in certain situations.best of luck.