The softer resale market needs to be a factor in your decision making process and never try to force a deal to work by shaving costs off your reno estimates or hoping for a bigger sales price . . . never works out

The best recommendation to anyone flipping especially in today's market is to over estimate the timeline especially when dealing with hard money which can kill you especially if you run out of time. 

Just make sure you’ve got some backup (photos, estimates, etc.) so if the IRS asks, you can show how you came up with the numbers.So yes, you can bonus in 2025 and still demo in 2026 with no problem—the tradeoff is whether you’d rather have a bigger upfront bonus depreciation now, or a bigger demolition loss later....This post does not create a CPA-client relationship.

Rehab Budget & ARV – A clear scope of work and after-repair value estimate are key for fix & flip loans.Entity Documentation – We will require an LLC, have your articles of organization, operating agreement, and EIN ready.For first-time borrowers, transparency is important.

- How will you estimate & budget so profitable?

Get line-item contractor estimates (not just a quick inspector note) so you know 1- and 5-year capital needs.Unit mix & rents vs. comps.

Does anyone have a ballpark estimate of the cost to build a new side-by-side duplex in duplex which is 3–4 bedrooms, 2 baths per side with each side being approximately 1,500 square feet per side with a 1 car garage and a basement?

They will develop plans and estimates.  

I agree with @Alexis Sostre - tree through house = increased risk & that return is not commercerate to the risk taken on... your contractor estimating is giving his best guess but there's no telling what he could find. 

The estimate can be off which would sway things.