You can start to educate yourself on the individual components; how much does it cost to paint on a per sqft basis or what is an average kitchen remodel.  

What can I expect for timeline, potential issues, rough costs? 

In reality it is costing you more. 

Those situations go bad more often than not, costing you money and the friendship.

Typically starting with a smaller rehab budget of $50K or less (maybe a max of $75K) and avoiding a 1 to 1(or higher) ratio of purchase to rehab costs is recommend when you are first starting out. 

I think it just benefits current owners. our replacement cost variability just went up a lot for the next 4 years.

They have cost my business tens of thousands of dollars and countless wasted hours of follow ups and missed opportunities.

How much is the rehab going to cost, what's the ARV going to be, and how much will the property rent for?

Since rental losses are typically passive, the best way to offset W-2 income is through Real Estate Professional Status (REPS) (750+ hours) or Short-Term Rentals (STRs) (100+ hours and more time than anyone else managing the property), which allow real estate losses, including depreciation, to offset active income.A cost segregation study accelerates depreciation, generating large upfront deductions.

The process from start to finish would take four months and cost ~200k to build, with comps in the area around 355k-lender man said, refinancing would take six months as most lenders wont refinance a property unless its been built for six months, affecting the strategy to get paid out from refinancing quicker and closing out on construction loan-The property would not appraise at comps value, but at the cost it took to build, affecting getting paid out from the refinance.