If you're going to spend $ on a raised bed, you could build it out of landscape bricks. If you don't use mortar, you can change your mind about the shape later, move the whole thing elsewhere especially if you move, they don't warp like wood timbers, look great, and are not a permanent commitment.
I've examined a lot of HOA documents and they are all different. If the closing company did their job, it's not something a buyer would not know about before the sale. HOAs are not foisted on unsuspecting or unwilling buyers retroactively. Buying a property in a neighborhood with an HOA is a choice a buyer makes when they purchase.