I also have more than one car (not including the daily driver), there are a couple of issue to consider that I have worked through;
1) Storage, you need to be able to get both out with equal ease or you will find that you use the one that is easy to get out and leaving the other parked up
2) Cost, if you want both ready to go you need to keep them both with MOT and insurance, not generally a big cost but needs organising. In our household it seems at least one car a month needs an MOT or insurance etc
3) Car type, personally I wouldn't have two cars that are similar in use, for eg both 4 seat saloons or both 2 seat sports cars. For me they need to be different enough to make it a choice based on mood.
Hope it helps.
Ken