When do interest rates change? 

Without any cash it is unlikely unless you can find a 100% seller financed deal (they do exist, I just did one a few months ago).

They're doing an A-frame.

Are they a start-up, do they have any operational, how do they do at it, etc etc.. 

do you have an offer from a builder currently and by builder do you mean your house is a tear down and rebuild.. or just a rehabber who is looking to rehab the home and flip it ?

.: Someone asked me about a Due on Sale suit I was involved in and it reminded me of the many encounters I've had with trying to buy pre-foreclosures and do SubTo.Some of these brutes are big, ugly, scary, mean and volatile.

Feel free to reach out or send me a message be happy to walk you though it or tell you what to ask for and how to know in advance you can do either option. 

How do I find out what area/lands development companies will want to purchase in the future? 

Quote from @Julia Havia: These are big projects and be sure that you are doing it all within the city scope of what they want for the property.

Knowing what NOT to do is often the most valuable advice!