Simply my own opinion, and what I'd do in your situation:
Because your goal is to have multiple homes paying for themselves (my paraphrasing), I'd start buying close to where you live.
There's at least a "small" emotional tie to the beach home ... and it's a distance away ... and I know it would be cheaper for you to rent for a week every 6 weeks than it would be to try to turn the rentals of your lovely (investment) beach-house into a pretzel to make it work on both sides of the ledger sheet.
I'd accumulate a couple/few good solid rentals CLOSE-BY because if you're the property manager you'll need to be around (and would you be hiring a property manager for the beach-house? I'd say renting it with a 4-hour drive as well as to see what the problem is and solve it will get old fast).
Then, after you've got some cash go for the trickier one ... or not. I happen to own 2 condos on the ocean in a luxury condo building. I have to book my 2 weeks in the summer in January or February ... or sometimes I'll choose from what's available if I leave it until March or April. And I can't help but think of the income I'm not receiving because I'm staying there for 2 weeks. ;-)