I have a home daycare and I have 2 kids. We love our easel and use it ALL the time. Some kids some to care having never painted before. Over a relatively short amount of time they all love it. And it's good for their artistic exploration and fine motor skills, (brush painting helps develop skills used in handwriting).
I have purchased 2 IKEA easels, but I don't have a "paint friendly" place in my house and (though they are well supervised) I give the kids a lot of freedom with painting. I left it outside and it didn't weather well. For the cost and the flexibility and for only 2 kids, the IKEA one is a bargain. You can do chalk on one side and dry erase on the other and/or you can tape paper on the dry erase side and paint. That's mostly what we used it for. It has a handy little tray to hold paint cups and paint drips. You can also save your floor/carpet by putting down a tarp.
Most recently I bought a 2 sided acrylic and metal easel that it designed for outside/inside. I got it through Discount School Supply. I love it! It's sturdy and easy to clean, however it doesn't have a place for a butcher paper roll and you have to just use paper or paint the acrylic and save the picture by putting paper over the wet paint like relief painting. I also like it because it has an adjustable height option. For bigger kids you can use it as it, but for smaller ones you can lower to their level.
You could also consider getting an easel that is flat and attaches to an outside fence or and indoor wall. (I believe that I have seen those through Discount School Supply also.) Then you can just roll it up and store it when you aren't using it.
Good luck! Painting is so good for kids. It is messy, but so worth it!!!