Sick ragdoll kitten...help me decide what to do!!?

I have been offered a 20 week old ragdoll kitten but the lady giving her away says she has a runny nose and eyes. She has had one set of shots and she doesnt know whats wrong with this kitten. I have two very healthy cats...a Devon Rex and a Ragdoll...all current on vacc's and happy healthy girls. I know if I take this kitten she will need to see a vet long before I bring her home...IF I even go through with this. What bothers me is that this lady doesnt want to spend the money to get a diagnosis and I am afraid what will happen if I DONT do something...this poor girl needs medical help but I am not willing to risk my own cats health...what do I do...any ideas of what might be wrong with this kitten. I could take her to a vet tomorrow but I could get myself in over my head if she is really sick...but I hate to just leave her getting sicker and sicker...ack..what to do??