It's not unreasonable for them to ask about your sources and uses/financing plans. If your plan is to figure it out when it is under contract they'll want to know how many deals you have done where you have successfully raised funds after a deal under contract, and how much equity did you raise. The market right now is incredibly competitive and is a sellers market. As a seller, if I have multiple buyers bidding at around asking, even if you are the highest bidder but there are two others that have any sort track record of closing, who would you sell to?
I would have a good idea of where your equity is coming from, they don't need to be fully committed but you don't want to start having conversations about who you are and what you do while you're in DD. I would go over underwriting/analysis of several prospects with potential investors, even old deals, to see if they would be interested in that type of investment. Once they're on board with the strategy, then you can even tell the broker that you have x number of investors on the sidelines waiting for a deal. You still have the line up the capital, but you want to have an idea of what the capital stack is going to look like before going in.