Why care what the broker is making from YSP, rebates, fees, etc, as long as they get you the best deal (including rate, fees, pre-pay penalties, etc)? You do need to get quotes from multiple lenders/brokers to know whether you are getting a good deal.
The key is finding a reputable broker who will give you an accurate and honest “Good Faith Estimate” of the loan costs in writing.
Beware of shady brokers who will bait & switch borrowers by offering loan terms they can’t deliver on. You don’t find out until you are escrow that you can’t get those great terms/rates anymore. The broker will usually blame it on the lender. At this point buyers are vulnerable and will often pay a higher interest rates, etc to save the deal.
A good broker can save you a lot of leg work and often find better rates than the big banks offer. As long as the financing goes through, it doesn’t matter much if the broker uses some flaky lender that will be out of business next year. It will have no impact on you. However, if you’re on shaky financial ground and think you may require a loan modification down the road, then it may make more sense to use a blue chip lender.