Hi Peggy,
Check out this site:
www.lab-retriever.net (it's a message board like YT is) you will find a wealth of information and possibly some for sale in your area in the price range your parents are looking for.
As to if labs and yorkies get along - so far, mine do. We got a female black lab puppy 2 weeks ago. It took a few days of "warming" up to each other but now, Gage and Mae (the lab) get along great - Gabby, who's set in her ways and deserves to be at 10 yrs of age, would rather see her be gone than to be here....lol!
I'm sure others will chime in as well. Best of luck to you!
p.s. admin, if I shouldn't have listed the site, please edit for me and my apologies in advance.