I would like to create a For Sale By Owner site for local Owners to sell there onw property with a Subscription for adding a single Property to the site with 5 photos, is this possible with the Property Agent Module

Hey there, I'm a new user to Ventrian, but I can answer your question, YES!

I am building a similar site, except for vacation rentals by owner.

Yeah it's very possible in my opinion.  If you're in the US, you might want to get a service agreement with a MLS 'provider'.  There are several companies that is willing to do just that, and it'll get listed in realtor.com as well as the local mls.