Yeah, I also don't understand how buying a house within one's own means is gentrification. Is the definition of "afford" different between your "very poor" neighbors and you, the "software engineer"?
OK, I guess maybe the original point was that there are super-cheap and super-expensive houses, and software engineers could afford something in between. They have to choose a poor neighborhood where they are wealthier, or a reasonably-priced but distant suburb.