I am assuming that even if you strucutred it with a higher purchase price (85% of value) and pre-paid rent it would potentially still be frowned upon.

The signing parties are "stopped" from saying anything different after they sign the letter.Each Tenant Estoppel Letter states the attached copy of the tenant lease is accurate and was signed by the tenant, there are no other written or verbal agreements, the tenant has paid rent through a certain date, and there is no prepaid rent other than the current month.

I have some of the required funds in a HYSA, but will most likely need to draw from another account and I'm curious which method is the most efficient in terms of taxes/capital gains, penalties, loan repayments, etc.Based on my previous transactions in the market, I estimate ~$45k cash to close: $20k for the down payment, $15k for closing costs and prepaids, and $10k of starting reserves.

It sounds like the Title Co. was not aware that the tenant prepaid rent and just prorated the current rent for the month of closing, so agree if they had no knowledge of it, would not have ever gone on the settlement statement as a credit to the buyer and they likely will not do anything post closing to help obtain those funds. 

Interest rate on both vehicles would have to be {near} identical or the amortized, fixed rate note would need to be at a higher rate than the LoC.In my above post I mentioned the "borrowed lump-sum" approach being necessary if the terms of your mortgage note were such that it could only be prepaid on its anniversary {don't know if such notes still exist}.  

So unless im prepared to lawyer up 3k just to try and get some of it back the answer "just walk away from your deposits, im trustworthy" doesnt work for me.I have prepaid for work from big names, Lowes installs etc.

My thoughts are to do an addendum (but not sure how to word it since she will have pre-paid her part until may) and let them figure out the security deposit between themselves at the end of the lease.

This is correct, but that .5% is IN ADDITION to all the other closing costs associated with a refinance (Title/Escrow Fees, prepaids, and depending on the bank, Underwriting / processor costs) - so in reality it can be a little more expensive to refinance with IRRRLs.

I have already shopped insurance, and the sellers are providing $5k towards prepaids/closing costs. 

Financing provided through this program is only available for properties located in Michigan or Florida.Available Product Type: SOFR 7/6 ARM, SOFR 10/6 ARMLoan Amount: $766,550 MaximumLTV: Purchase and No Cash Out Refinance - Maximum 99%Prepayment Penalty: NoneLoan Assumption: NoneEligible Properties: 1-unit dwellings, attached and detached condominiums, PUDsEscrow: An escrow account must be established for property taxes, and flood insurance, if requiredUnderwritingNo Private Mortgage InsuranceOccupancy – Primary residencesMinimum Credit Score - 700DTI – Max 43% (UW/Mgmt exceptions up to 50% with minimum 3 documented compensating factors)Student Loans – If in deferment, no qualifying payment requiredDown payment of 1% must be borrower’s own funds, while closing costs and prepaids may be gift fundsAttached condominiums require a 10% down paymentEligible Borrowers – Protect and serve heroes are defined as employees of public or private education institutions, employees of medical and healthcare organizations, all first responders, and active or former military personnel.Servicing: Retained