I disagree slightly on using fall-through rate as a headline measure. Without the number of transactions and reasons behind failed deals, it can mislead. Ask instead what the agent does when a buyer withdraws: whether backup interest is maintained, who contacts earlier bidders, and whether...
Convert every proposal into total euros at the expected sale price, then list what triggers extra charges. Ask what is payable if you withdraw, no acceptable offer arrives, or an agreed sale falls through. A low headline fee is not comparable if photography, negotiation or closing work is...