Realistically: What should I buy / what can I afford?

Looking for something boring, but preferably quiet and reliable. I don't care about brand. I'd like to be able to drive it for 5+ years, at a rate of 10-15k miles per year. I don't really know what my budget should be, I only make ~$180-250k depending on performance of my business, at least that was last year, so based on the financial samurai's 10% rule I think that puts me at ~$18,000 limit on a car. I can pay cash for that.

TLDR:

Tell me what to buy: I prioritize reliable/affordable/quiet on the highway over fun.

Budget: $18k

Should last 5+ years at a rate of 10-15k miles a year.