With your singlehanding requirement you should be looking for boats that have all the major chores close to hand. Primary winches should be within reach of the normal helm position. A furler will greatly ease use of genoas, especially of you get into a mid-to-high 30s footer from the IOR era with their large masthead rigs. Wrestling a large genoa to the deck, even hanked is quite a chore in a breeze by yourself. If it's in a foil its harder still.
You might say, "I'll get an autopilot so I can run all over the boat while it drives itself".. Reality is that few autopilots will handle all conditions well, and the fact that it is there will encourage you to leave the cockpit to do this or that (skirting, tweaking a leech line etc.) Human nature says that you will not be clipped in EVERY time you do this and so you put yourself and your boat at risk. We find that the Autohelm is really only useful when motoring or while setting or dousing sail.
Avoid boats with excessive control lines like running backstays, keep it simple.
I'd look for newer designs that put more power into the mainsail, e.g. fractional rigs or short J-dimension mastheads to ease the tacking. Best of all try to find a boat that doesn't need overlapping headsails, that really makes life easier, but there are not many of those around.
Without a lot of expensive gear, size is a limiting factor for the singlehander. Keeping the loads down to a manageable level also coincidentally keeps the costs down across the board. Those costs, by the way, vary greatly with boat size and so can't be generalized very well.
Finally, given your intended mix of coastal cruising and potential offshore, I'd still favour a well-found performance cruiser type over the traditional heavy offshore boats. Good Luck.