cupid.net looks like a starter site. The About Us and other pages aren't filled out. The domain is listed for $29,000 on Sedo. They do accept offers, starting from $20. If you can get it REALLY cheap, consider it.
modeling.net appears to be owned by Explore Talent, who has 3.5 MILLION followers on Facebook. I'd say 0 chance they sell just the domain. They may sell the business for the right price, I have no idea. If they do, it won't be cheap. You had better have a LOT of experience in this type of business to even consider it.