You can do as little as 0% down and maybe even get money back at closing if you can implement seller credits into your offer during the inspection period or prior to going in contract. 

Quote from @Nick Grassi:Not sure about Florida, but my experience with solar.. 5 years or more ago, buyers would take over leased panels and not have any issues with getting a solar lease from the owner prior to them.

Documenting erosion severity, prior concerns, and the contractor's assessment could help support a claim. 2.

Yep, I ALWAYS recommend doing an inspection prior to close. 

if you are fine with that, then the Sub2 buyer should simply instruct the attorney and/ or title company how they want to take title of property.

It's definitely something you want to resolve and really title should be able to resolve it prior to closing as part of the closing process.If you are looking for a resource who might be able to help, look up Jon Jasniak.

Recommend cash for keys here (like you already tried) and getting them to sign a termination of lease.If the lease period ended and they are on month-to-month typically you have leverage (depending on what your lease says, or local laws) to end the lease at the end of the month given prior notification.

No where did it say these were projects from a prior company he worked for. fake it till you make it.. but everyone has to start somewhere :)

It is normal to get cold feet but the main thing is to do the best due diligence you can do prior to going under contract-  "Pre-DD". 

It can be done DIY but takes a lot of research and groundwork prior to purchase.