What is your required return on investment?

Unless my assessment of your situation is wrong based on what you've provided, you will be required to utilize Schedule E, and cannot classify this under Schedule C. 

I have extensive knowledge of working with Pinellas county and the city to get your Airbnb in good standing with their codes and requirements, along with access to many tools and systems to generate free analyses for you on any property.

I do think that a few of these big things will require a loan - the paving for that one multiplex is estimated at around $30k and the septic tank issue for the large multiplex would likely be even more.

The ones that require leverage are not the greatest though (just like when leverage was cheap they were great investments)

It seems like you would have the funds required to take the HELOC or just from investments.

Give them the minimum required non-renewal advance notice and be done with it.

Be aware that the lead paint laws require you to delead rental units within 90 days of closing in order to not be liabe for past tenants.

A builder has special requirements when the financing comes from an FHA loan.  

Required down payment is typically 20-25% depending on FICO, property type and level of experience.