Looking for small, inexspensive, clean places to stay near (walking distance) the beach, pubs, restaurants, etc. Also a place to look up small, inexspensive (maybe fixer-upers) real estate (homes)for sale within miles of the beach.

There are several rental companies on the island that can hook you up with a place that is near the beach, pubs, and restaurants.  I think the best area for that would be toward the South end of the island.  I would suggest that you call Tybee Vacation Rentals at 912-786-5853 and asked to speak with Kelly Doyle.  She can direct your call to the appropriate person. 
If you are interested in a fixer upper, you might want to contact a real estate agent on Tybee.  My suggestion would be to call Bonnie Gaster at 912-786-5759.  She knows Tybee very well and she can hopefully hook you up with a piece of property.
I hope this answers your questions.  Please feel free to contact me again if you need further assistance.

thank-you!