Cheap lead may be hard to find. I got lucky when I found a guy with a wash tub full of wheel weights and several buckets of lead shot he no longer wanted. A year ago, commercial sources of lead ingots were $2+ per pound. Probably higher today.
Others might not agree, but I have it in the back of my mind that if a guy could build a boat, he could also salvage (recycle?) one. There are literally thousands of derelict boats strewn up and down the coasts and many of them will have at least 1,000 pounds of lead still clinging to the bottom of them. Beyond that, they may have all manner of cleats, blocks, pintles, gudgeons, anchors, etc. and other useful bits that might be put to use on another boat, not to mention some mahogany or teak trim still hiding around inside. For a true derelict that will never sail again, yards and owners (if you can find them) may be happy to see you show up. I'd check the legality of title, and have a plan for the carcass (chop saw and dumpster comes to mind), but if you solve that, it might work.
BTW, I would not limit my search to yards. I have observed these derelicts as far as 10 miles or more inland from large bodies of navigable waters. You see them hiding behind barns, under shade trees (sometimes with trees growing out of them). When I have asked about those, the answer has always been the same........."you can have it for free if you will get rid of it".