Good info sir ! I had explored the option of using your backstay as a inverted V dipole except as you said they are expensive and the work to have them installed in pricey also.The insulators alone are around $500. a piece and you need two of them. The one thing I found it is hard for the auto tuner to tune the "lower" bands.
The verticals work ok. The best set up I have found is buying a commercially made wire dipole. Buy a good one, they are around 150 dollars. This will last your forever. My fav is the Buck Master dipole. They tune very easy and will withstand the marine elements. Just simply attach a halyard to the center of the dipole and hoist to the top of your mast, tie off one side to your bow and one side to your stern and attach your coax cable before hoisting. Thats it !
As far as buying a used radio, its a good idea to buy from a HAM site such as QRZ.COM
, eham, or ham radio outlet. There are "HAMfests" where you can go and see the radios first hand that people are selling and try them out. Ebay makes me nervous, however thats my personal opinion with no experiences to tell. I bought my first one in excellent condition for $350.00 . Still use it to this day, everyday. Even if you buy a brand new one you can spend as little as $500.00.
Grounding....critical item ! The cool thing is sailing in brackish or salt water is the best ground plane you can have. The water that your sailing in is your ground plane...how cool is that ? I have found that grounding your radio to two or more points works very well. I used the metal shaft mounting brackets. The shaft goes straight into the water. The motor mounts and the seacocks are great. Basically anything metal that touches water is a good spot.
So, in recap, a good new/ used HF SSB radio, an auto tuner if the radio doesn't already have one, good coax cable...you really need LMR400...its the best. Then you need a good commercially made dipole. With all these items in place, you will have clear and the absolute best communication possible.
So you can have everything you need for under $1000.00 easy ! Get a laptop and free software now you can receive all your weather faxes for free !!