I bought my first car on Craigslist back in 2011. Then my second used car on Offerup. Depending on your area it can be the highest web traffic website/app. Always verify that the person selling the car is the registered owner and its a plus if the registration is up to date. Some common red flags are people selling a car with "bill of sale only" or saying the car just needs a battery or new spark plugs. You can end up towing a car home with a blown engine that you are unaware of.

I've had good luck on Craigslist. Offer up seems okay, if you can find one that is not a scam. 

Family’s friends, friends’ family, friends’ friends.

Autotempest.com

a trustworthy mechanic who knows people that have good cars and want to sell.

AS a rule of thumb: Do NOT buy/sell a car from/to a friend. 

Thank you I have looked on offer up and Craigslist and majorly are high mileage 175000 and looking in poor cosmetic condition.