They have sent me a letter in the mail asking to buy my lot for almost double what the local values are so I'm not sure if this is a scam or just to good to be true.

Is this generally true for all insurance companies? 

Be cautious of any promises that seem too good to be true, especially around funding or guarantees of success.

This is especially true the more people you try to cram under one roof. 

And since I am brand new to a lot of this I don’t know what is too good to be true.

The true definition of "owner financing" is that the owner of the home is providing the financing to acquire a property.  

If that was not true, he would’ve done it instead of saying it.

They would have to foot the bill and also pay for the removal (up front) - because maybe they will work the disposal correctly, but there will be a next tenant - so that decision could have expensive consequences for them.When you present them with the true cost of install and removal, it may not be that important anymore..

The same is true for any property in the world.  

Though I appreciate the idea of finding online resources and studying them, I find that a curated, tried and true formula (if it works) is much more worth my time than spending time trying to find which resource works best and then spitballing the ideas until something sticks.