(Currently our rebar supplier is behind 2+ weeks and these materials were ordered 45 days in advance). 

However, he asked me to sign a one-year Exclusive Right to Represent agreement, as presented to him by his brokerage.His interpretation is that it applies only when he materially assists me, but I think the boilerplate brokerage language he was given reads much more broadly:"If during the term of this Agreement Buyer enters into a contract for the purchase of Property through the services or efforts of the Broker or Buyer’s Brokerage Firm, or by or through any other persons during the term of this Agreement" (emphasis mine).My concern is that, under my interpretation, if a fellow real estate investor wants to unload a property or if I get pointed to an opportunity by a former agent, colleague, or friend, this agreement could create an obstacle to moving forward with the deal.In the end, I didn’t sign.

Rehab costs and ARV (After Repair Value) are key parts of evaluating deals, so it’s great that you’re diving into these concepts early.For rehab costs, creating a rough estimate starts with understanding the scope of work and local pricing for materials and labor. 

Focus on tax-saving strategies such as cost segregation studies and bonus depreciation to accelerate deductions.By qualifying as a Real Estate Professional (spending 750+ hours annually and materially participating), you can offset your wife’s S-Corp income with real estate losses, reducing your tax liability.

I would also add, a contractor that you can buy materials for and they know how to put them in with little to know direction (reduces the management time of the project).

Some of the materials we choose and asked him to pick up (such as flooring) he replaced with low quality materials, I assume to keep more of our money for himself. 

And sometimes, we are not materially improving what you could have done  yourself. 

I understand the basis is all the remodel cost or labor and materials. 

Because it's a material fact to them.

There’s a rigid plastic type material that’s used in dairies and on farms that I’ve seen used.