Even before you make the decision you want to buy a guitar, even if you have the time and the money, you have to know that playing a guitar - or any instrument - is an investment in that time and money. You have to be realistic with yourself and know that you will not be good at first, and it may even be frustrating at times. If you persevere through that frustration and keep a positive attitude towards it, it can be very rewarding.
I've had many friends of mine become very intrigued when they saw my ability to play guitar flourish. A few of them were so motivated that they decided to go out and buy a guitar of their own and learn to develop the skill. I will tell you right now there were a lot more who played for a month, got tired of it and quit then who saw through to the end to become a real guitarist.
I believe this to be a story of many aspiring musicians. They tend to get very excited when they see how rewarding a thing like playing guitar can be and they go out and buy their instrument and when they find that they can't play it just like their favorite musician instantly they become very discouraged. You have to step away from that anticipation to be that developed in the skill and really look at it as an investment of time.
Music motivation can come in many forms. Before that can come you will need to take the time to practice, practice, practice! Once this has set in to your mind and becomes something you really strive for, you will start to notice yourself getting better and better. Try not to focus on the big picture of when you will be shredding with the likes of Jimi Hendrix, but think to yourself "wow, I remember when a week ago I couldn't even play that