Go on Youtube and check out how easy it is to brew in a bag.
Start off cheap with a pot on your stovetop, a bag, and a partial mash recipe; use some grain and some extract. You'll need a few other things, like a carboy or a bucket, a funnel, an auto siphon, a hydrometer, a thermometer, some bottles and a capper and some star-san. Get a few simple brews done and move on from there.
I'd start off brewing 2.5 gallon batches, you can use a 3 gallon or a 5 gallon fermenter. The Brooklyn brew shop Beer Book has lots of easy recipes in 1 gallon increments to get you started. Note that book doesn't have any extract brews but it shows you how to get started with all kinds of styles.