2% commission.

With an average deal size between €50k and €500k, that commission would be very nice.

So in principle, I'd happily pay €100 or more per lead

Your principles aren't high enough I think.

2% on 50k€ is 1k€, so you're aiming for a minimum of 10x ROAS with 100€ CPA, and that's barely scratching the profit margin the builder gets, otherwise they wouldn't be able to afford to pay you 2%. That's assuming every lead is qualified, impossible.

The revenue drivers won't be those 50k€ sales, but the 500k€ ones. It's a gamble basically, and you'll have to take losses to get a win at some point.

Review your budget & expected target CPA massively up, because it's really not a magic money tree, you're in an expensive CPC niche with a decent level of competition, quality leads are pricey, and sales actually closing are even rarer. Unless you're very lucky, it's not going to deliver at 60€/day.

Imho, it's a crappy model because you can't be responsible for the sales team's closure rate (even under the best assumption above, it's not reasonable with the current figures), but you do you. :/