Frankston has been kind to us over the last couple of years, exceeding our expectations.   Its really hard to answer your questions without any info in regard to your aspirations, budget, constraints etc.   

We have a place in what some people would think was Frankston North/Karingal, but is in a newer development and attracts tenants easily at a good rent.  A kilometre or two away, across a golf course, things look a little tired and dowdy and of course cheaper.  Great place to hunt down fixer uppers ,  but we arent in that game at the moment.