@Barbara BertaDoing a 30 min. consult with a Real Estate Attorney will probably be well worth the cost.  

It’s costing you thousands of dollars post-tax plus wrecking your DTI. 3) sell your current home tax free and buy a duplex or fourplex.4) AGAIN: figure out the ownership structure and the breakup structure.

If a buyer is offered a 2-1 buydown (starting at 5.25%, increasing to 6.25% and then to 7.25%) with all closing costs covered except for $3,000 (to be paid by the buyer) on new construction through the seller's preferred lender, and signs the purchase contract in April 2024, the house will be completed by the end of September 2024.

Is there an order of magnitude we can use to estimate what it will cost us?

Depending on how much there is and where will affect the cost to get rid of it.

That's three months of mortgage and utilities, the cost of flooring, and the cost of painting.

EDUCATE YOURSELF - yes, it will take time, but will lead to a selection that better meets your expectations & avoids potentially costly surprises!

If you provide a scope of what you are demo-ing, you may have better luck with someone's experience to comment here, but costs can vary regionally, so a local contractor would give you the best actual estimate. 

CPAs seem to be very expensive costing thousands of dollars!

Another option is to raise private money loans for the downpayment and set-up costs of a STR.Above all I would make sure the neighborhood can support two STR.