Is it not expedient to send a sample chapter of a novel-in-progress, to find out where interest might lie, rather than wait until you've got it all done, and then maybe spend the next five years sending out queries?
Since we agents have such heavy reading (and the lion's share of that reading is material we won't ultimately take on) you shouldn't go on a fishing expedition with a work-in-progress (unless it's non-fiction, where a proposal/sample can be enough to sell). Either way, you're going to finish your novel if you're committed to it, so my advice is to use submission energy wisely. Most agents won't offer to represent fiction without digesting the complete project, so you don't stand to gain much from reaching out prematurely.
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