Tips for buying a used car under $6,000

I'm in need of a car. I can only spend about 6,000 dollars and I know near nothing about cars (as in, "I'm still trying to figure out what a cylinder is" nothing). Different forums say that spending 6 grand on a car with around 150,000 miles is stupid. But all the $6,000 and under cars at every reputable dealership where I live all have 150,000+ miles on them. There's actually very few with only 150k miles on them, most are in the 200k range. I know absolutely nothing about cars, nor do I know anyone that does so I really can't do a private sale. It will have to be a reputable dealership (not "Auto4Less" or something like that). What should I do? I'm in the market for really anything that works. Probably Honda or Toyota. Anything that will last a long time and is cheap to maintain.

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