now I probably wont be able to find a tenant till mid september/october.

If that wont work then get out of the sale. 

If you're mortgage is lower because you were able to get the house at the right price, with the right terms, that 50% for expenses wont seem so daunting. 

Eventually you wont need it and you will be able to come up with more accurate repair numbers.  

If you try to grow too fast without enough money, experience or connections, your foundation will crack, and you wont have any money to repair it.

In Maryland you wont make much doing rentals (Other markets you can like NYC and Boston) and you have a high liability with rentals.

I wont claim to be a master pricer.

I guess the danger is that if you price to high, not only will you not get buyers, but banks wont appraise.

I do know that there is a 6 month seasoning period for traditional banks.I have tried with few small banks and mortgage companies and got burnt with multiple credit pulls and non attentive bankers taking 30 days to come back and tell me they wont do loans for investment properties (even after I had clearly mentioned it in the application). 

As with most real estate you have good and bad seasons and when it is bad everywhere vacation rentals can suffer.