I have one alpha-reader who gets chapters in rough form. And then, when the first draft is finished it goes to my agent. (I sometimes do a little fill-in work to better work transitions between scenes or add scenes that I realized while drafting needed to go into earlier sections, but that doesn't happen with every book and there's not a full-on second draft prior to the agent-read.)

However, the alpha-reader rarely gets second/third/fourth drafts (if they occur) because they've already seen the first draft. (I show them new chapters, but not every revision.) So they get a first draft and then usually a copy of the final MS to read if they want to. But, I'll also say that my first drafts are usually fairly clean spelling/grammar-wise. Sometimes the plots are a mess, but the prose itself is not particularly difficult to read. When I was still in my early stages of writing and had issues with writing cleanly, I did not show folks first drafts because that would have been a waste of their time.