You can only build hotels or factories if you are in the same city as the intended development and of course, you need cash to build them. Arriving at the airport you can see the going rate for hotel builds and you can keep building as long as you stay there. Factories are expensive, possibly too expensive in all but the least risky situations. To be in the required city, you have to fly there. You can fly as many times as you like in a turn, so to squeeze in that all important hotel contract in Hong Kong, you might fly from one side of the board to the other in three legs.
Money is short, and remains so until late in the game.
You can sometimes survive the third phase on cash alone, but more often than not you will be running loans for the whole game. It therefore makes some sense to take out loans early in the phase and to try and keep within budget to avoid an embarrassed return visit to the bank manager. You then decide whether to repay or extend your loans - extension means even higher amounts of interest payable. Or a mix of the two. This clever twist, and one that will hopefully lead you to the same overall conclusion as me, is that the cities do not develop on an ever-improving trend.