Amy,
There are a number of creative ways to finance a home . Rent to own would be one of the more common. see if seller has interest. I think by giving yourself an option you are risking less in the long run.
For some reason if the STR doesn't work as you thought it would than you walk away minus any small money you may have put up for the option.
It would be considerably less stressful than having bought the home and now being in a situation where you want out of the home . Your purchase costs would be gone , sales costs gone and even possibly the home Devalued .
Most of the time landlords wont allow subleases and will likely not allow Airbnb . However if you intially presented it as Rent to Own , they may be more open .
I would offer the landloard the rent they are asking plus An Option To Buy deposit . He gets a few extra bucks - $1000 -$5000 depending on market . You get freedom to act as you want . Suceed @ Airbnb, or watch the house appreciate and you execute the contract . If it goes the other way walk away , and leave the deposit — which would be much less expensive than having purchased a home and than having to unload it .
I think it’s a win / win
What city are your beach homes in ?
I have a home near USF and would consider a rent to own tenntant / buyer with terms above .
All the best