new to this

Hey Biggie welcome to the forum. Everyone has different motivations for motorbicycling. As far as building your own or buying one already built. It depends on mechanical and building ability. Building it yourself would probably save you some money. But if you don't have the ability to finish it then you have wasted money. There's lots of help and info here.

I thought I would use mine to commute to work and save some gas money. But I realized a few days a week I needed to go the bank and didn't feel secure going back and forth with bank bag full of cash and checks. So I'm back to driving my car every day.

So I would recommend reading all you can here and ask lots of questions. Then you will be able to make informed decisions about how you want to proceed.....

You could keep your car and save a bunch on gas money. Depends how far you have to go for work. The engine you most likely saw is a 2 stroke "china girl" or also known as "happy time" engine. The bikes with the engine can last a very long time if built right. The engines aren't built well in the factory and are known to be a jack in the box. You never know if you have a good one until you ride for a couple hundred miles. If you follow a guide from al.fisherman you won't have issues, but it requires a bit more mechanical aptitude

There are alternatives that can last you a very long time. You may consider a friction drive (mounts over the rear tire) from thatsdax.com. Any member here will recommend thatsdax. It may not be the best website but if you call Duane you'll see why. Best customer support out of any vendor out there.