b2b saas is a pretty competitive space in the PPC world. It sounds like you sub-vertical is even more competitive, but that would depend on the keywords you look to be competing for.
If you’re up against the likes of Stripe, Quicken, PayPal etc. (speculating here), expect high CPCs.
It’s good you have a specific goal and timeframe. In terms of meeting that goal, it would be helpful to know what your typical conversion rate is. What percentage of website visitors ultimately become qualified leads?
If you don’t know, I’d start digging through your data to get an answer to that question ASAP.
That will then help you determine a ballpark amount of ad spend you will need to hit that target.
For the sake of simplicity, say your conversion rate is 1% historically, and average CPC in your space is $15. $1,500 is what you would want to budget to get 1 qualified lead. To get to 50, you’d need to budget $75,000 if you continued at a 1% conversion rate.
Of course, a good PPC agency will be focused on improving your conversion rates and lowering your cost per lead.
If you know your numbers well, your conversations with prospective agencies should be easier. If they don’t have a straightforward approach to getting you a positive return on your ad spend (ROAS), I wouldn’t waste your time.
P.S. my agency specializes in PPC for b2b saas companies, which is why I bothered responding here. Let me know if you have any other questions!