A few years ago, some acquaintances of mine bought an apartment in a neighborhood that was "about to explode" according to the sellers. They convinced them with the same old pitch: new projects, a metro that supposedly would arrive, shopping centers. The apartment cost a third of what something similar went for two neighborhoods further south. Well, five years went by and the area did grow, but not the way they expected. It went up, yeah, but only about 15% in that time. Meanwhile, they were paying maintenance, property taxes, and their money was stuck there with no way to touch it. If they'd put that into the more expensive apartment from the start, they'd be in way better shape today.
The problem is you've got two hidden costs that nobody mentions: the money you put in is frozen for years, and even if the neighborhood goes up, your fixed expenses go up too. Plus, the projects they promise sometimes never materialize, or they do but at a snail's pace. A cheap apartment in a developing area can be a good investment if you're buying it to actually live in it (so at least you save on rent) or if you've got enough cash on hand to afford having that money sitting still for several years. But if you're buying purely hoping to sell high in five years, you're betting that everything goes perfect, and in real estate almost nothing ever does.
I'd check hard what concrete projects are actually already underway (not "planned"), I'd talk to people who've lived there for a while to get a real sense of the growth rate, and I'd honestly calculate whether you can sleep easy having that money tied up. If the idea of not being able to touch that cash stresses you out, that cheap apartment isn't for you.