"One of the things I hate is when I pull up to the pick up spot and my rider has an infant. I do not feel comfortable having the baby on someone's lap, so I refuse the ride and everyone's time is wasted. I have considered getting a baby seat, but I really do not have the money."
This is a touchy subject for sure. You can shell out a few bucks so that you are prepared for these types of rides, or just decide ahead of time that you will refuse these. Child seats are costly, and might take a while for you to create a return on the investment. If you do puchse one, make sure to set it up with a big smile on your face and to make a big deal about it -- that it is an additional service you offer because you are the best. You are more likely to get their appreciation and most importantly, more tips.
Either way, make sure you err on the side of your state or country's laws, as well as the safety of your passengers.