The single best piece of financial advice I could give is to drive your car until it dies. The second best advice is to take care of your car.

Here's what happens. People decide that their car is warn out and they stop taking good care of it. See the damage on the side of your car? You didn't fix it because a) you didn't have the money, or b) it's old and you're going to replace it soon anyway. Right? Well, now you're talking about getting a new vehicle instead. That new vehicle will cost way more then it would have cost to just fix your existing car.

This is especially true in todays market. It is almost always cheaper to fix your existing car then to buy a new one. When it's not worth it, it's because the car itself is bad design, poorly made, etc. The 2007 Honda Accord is not one of those. It's one of the most reliable vehicles you could own. Maintain it like you'll be driving it forever and you will be driving it easily 300k miles.

Your catalytic converter is not an item that ever warrants your car being dead. Take it to a muffler shop and have them replace it, should be around $500. You might also have to replace the muffler as it gets rusted too.

I was 100% not interested until it said, "beer-brewing"

I've never had an issue buying things. From what I can tell on /r/scams, usually, scammers will try to pay you through a different app and not PayPal. So just require they pay through PayPal and you're probably fairly safe. For anything large: pickup in person and cash only will stop almost all scams.