If real estate contract to buy is terminated and accepted by broker, can the owner then feel free to sell property in Maine

It's difficult to answer your question definitively because it's not clear what you mean by "accepted by broker." However, most listing agreements...

There's no such provision applying to leases of this type in Maine.

What am I supposed to do now that I have become successor trustee of my father's trust holding real property in Maine?

You definitely need to have a competent attorney review the trust document and advise you about your powers and duties as a trustee.

What is my best, most cost-effective option -- if there is one -- that would get results?

You don't mention where this client is located. One possibility is Small Claims Court. In small claims, you represent yourself and don't incur...

What are my Maine rights?

His rights, if any, are extremely limited. Based upon the limited information you're provided, I would assume you are the only person named on the...

Can a town charge a new owner 5 years later for the previous owners tax liability

Probably. Your question doesn't go into enough detail for me to be sure what's happened here, but there are two possibilities that come to mind: ...