Is it illegal to sell paintings on the street in TX?

I don't know of any city or town in Texas where it's legal to sell anything on the street unless you have a vendor's license. You might be able to find a few buyers on Etsy, but don't get your hopes too high, unless you are a professional quality artist. Yeah, your family and friends might think that your works are great, but they are your family and friends. I learned this the hard way.

And you need to do the dog walking thing NOW, when it is hot, because now is when people don't want to walk their dogs. When it's cooler, they will want to walk their dogs, and you won't have as many customers.

The thing is, you have to offer your services when your customers most want and need them, not when you find it's most convenient for yourself. For instance, if you work in food service, you won't get a meal break during the breakfast/lunch/dinner rush, you'll get a break when most people DON'T want to eat a meal...say at 9 AM, or 2 PM.

In any city or town across America, you must obtain a vendor's license from the local authorities before selling on the street.

There's no state law against it. Check out your city ordinances or county zoning restrictions.

look at state laws, you might need a license to street vend.