I worked in banking for years and was a Private Banker with securities licenses for a time.

If the property is paid in cash and later a mortgage is secured does it impact the UBIT question above ?    

I explained to the seller that my offer contained a substitution of collateral clauses and I would be exchanging the note they held on the subject home with a note of similar principal and interest secured by a different property of greater appraised value.

The security deposit was $1,200, but here in Florida, attorney's fees and costs are recoverable to the prevailing party in cases concerning security deposits.

I’d appreciate some feedback on my current approach and advice if any.Here’s what I’ve done so far:Pre-Approval: I’ve secured a pre-approval amount and interest rate from an online mortgage lender.Property Analysis: I’m using the mortgage and STR calculators from BiggerPockets to assess the financials for potential properties.Neighborhood Research: I’ve been exploring different neighborhoods using Niche to get insights into schools, safety, and livability.AirDNA: I’m considering subscribing to AirDNA for data on occupancy rates and rental income estimates.Questions:Is AirDNA worth the investment for STR data?

I’m a new landlord in CA and missed the 21 day window to return the security deposit (I thought I had 30 days).

He sent me a contract which if I sign will pay him a fee of 3% of the money secured. 

I would want my money to be secured by a promissory note and mortgage on the property in question, and thanks to the advice from some on here, if the property in question isn't enough to cover it, I would need to attach a lien to other property to ensure I can get my money back. 

for sure that is always an option, right now i want to connect with more actual private lenders that want to move their capital at 11% secured by real estate 

Non-recourse loans are typically more common with large-scale commercial projects or through institutional lenders, but most lenders prefer recourse loans where personal guarantees are required.The reason most loans are recourse is that it provides the lender with additional security.