Get a digital of good quality and try to find occasions for practicing on an acoustic from time to time, and you will be just fine. First time I went from my digital to an acoustic piano it took a while for me to adapt, but now I just do it. Back and forth, no problems.
The difference between my digital and a grand is less than between an acoustic upright and a grand, IMO.
On the other hand, I do not advise you to buy a cheap digital with a plastic feeling and not the right action. You will probably lose your patience with it quite soon. The better models are of course "a bit" more expensive but keep in mind that the most expensive part are the loudspeakers, and if you plan to play quietly or with headphones you can go for a model with modest loudspeakers, that will bring down the price a bit.