Can a seller insist on being paid in full even if my financing falls through at the last minute?

It depends entirely on whether the purchase agreement includes a financing condition protecting the buyer, since there is no automatic right to walk away from a signed agreement just because financing did not come through. If the agreement makes closing conditional on the buyer obtaining satisfactory financing by a stated date, and that condition genuinely was not met despite the buyer's reasonable efforts, the buyer may be able to delay or terminate the deal under that clause without being treated as in default, and the seller generally cannot insist on full payment regardless.

If the agreement contains no such financing condition, or the buyer simply failed to secure financing they were otherwise expected to arrange, the seller can generally hold the buyer to the purchase price as agreed, and the buyer's failure to fund at closing is itself a breach that can expose the buyer to damages, forfeiture of any deposit, or a claim for specific performance. Whether a financing condition exists, exactly how it is worded, and whether it was properly satisfied or triggered are the decisive questions, so both sides should look closely at that specific clause the moment financing appears at risk.