If you're talking about the SAME property, it's called a lease-option. You're leasing the property with the right to purchase it. Or you could do a lease-purchase, in which you lease the property but you've committed to buying it.
If you're talking about renting one property and buying another, that's possible, too. One hurdle is qualifying for the purchase since you'll then have two monthly payments--one for the rent and the other for the purchase.
You will always pay more for new construction if you build. Watch for builder spec homes. They are always more motivated to let those go at a good price than when you build and they nickle and dime you on everything. Don't go into a builder unrepresented... they will hand you a Chili's gift card and make you think they are your best friend. They DON'T represent you... they represent the builder and Unrepresented Buyer Disclosure is one of the first forms they will have you sign, which basically says you are on your own for non-biased market advice and usually means they are making a lot more money behind the scenes. Call me before you make an offer and I will do a free Home Value Assessment for any home so you know you are getting a fair price. Also, buyers I represent, get all sorts of incentives. Besides, I am paid by the listing agent, so you have no out of pocket costs for my services.... more