Your $80K HELOC can serve as the down payment, as most lenders require 20%-25% of total project costs upfront.

The best scenario for the buyer buying subject to is to have enough money and good enough credit to qualify for a new loan at current rates should the due on sale clause be invoked by the lender  

We exclusively travel during non-peak seasons, so we would be looking to rent out completely during busy/peak seasons, and would stay at the place during slow seasonsQuestions for the experts out there:1. which development(s) tends to be the best for ROI/have the best occupancy rates?

You set your own payment terms with YOUR client and then find funding for them.The Capital Syndicate is a private lender firm that offers financing through their own company, but they also provide you with a list of about 150 other private lenders. 

How many mortgage lenders have you spoken with to get qualified and discuss allowable down payment options?

Did you work with any real estate professionals (agents, lenders, etc.) that you'd recommend to others?

Oversimplifying it just a bit, the investor profits from:- a non-refundable option paid by the tenant-buyer which gives them the right to purchase the property within their option period- the spread between the rent paid by the investor to the property owner and the rent paid to the investor by the tenant-buyer over the life of the option- the spread between the price ultimately paid by the investor when they exercise their option with the owner and the price ultimately paid by the tenant-buyer when they exercise their option with the investorClear as mud?

@Adedotun Kembi Most lenders will only lend a total of 65-75% on a rental and at much higher interest rates due to the higher risk.

But with that one lender I found I am not lendable due to not having proof of income for the last two years.

If you haven't talked to a lender yet, that's really your first step.