I am looking for help with estimating rehab costs and to help during the rehab period... 

I haven't seen anything under 200-250k all in cost 

Costs are up, but so are asset values and potential rent increases.

If you refi to a renovation loan by including the ADU costs + paying off the existing mortgage, would your total monthly payment be financially comfortable and agreeable to you? 

.); no more than 60-70 m2 (that's about 650-750 f2) to, among other things, lower renovation costs; 1-2 bedrooms, street facing and with a lift (if said apartment is above the second floor); with good bones, i.e., needs only partial renovation.

Will interest rates increase, which in turn devalues the same raw dollars of NOI because of increased debt service costs?

Keep in mind that refinancing involves closing costs and may require meeting certain eligibility criteria, but it could provide an opportunity to transfer the property to your LLC.Consulting with Legal and Financial Advisors: Seeking guidance from a qualified attorney or financial advisor who specializes in real estate investments and asset protection can provide valuable insight and assistance in navigating the transfer process.

Additionally, consider cards with no annual fees to keep costs down.

They said we low balled them, I told them they didn't and guess what, they received another offer near ours and at the end, the property didn't sell.Construction costs are high.

I wouldn't consider this an investment, but maybe a way to offset your costs.