It's all separate transactions.
1. Your parents give you money.
Gifts are not taxable to the recipient. Your parents will have to file a form 709 gift tax return, but they probably won't owe tax. Once you have the money, it's the same as all your other money, no matter how you acquired it.
2. You buy property.
Not taxable.
3. You carry the property.
If you generate income (from a rental, lets say) you report and pay tax on the income and can deduct expenses and depreciate improvements. If there is no income (vacant land) you can't deduct most carrying expenses, but you may be able to capitalize them.
4. You sell the property (future).
You will pay capital gains tax on your gain, the difference between your cost basis and the selling price. Your cost basis may be adjusted upwards by the value of improvements and capitalized costs and downward by recaptured depreciation.
#3 and #4 could be the subject of entire college courses on accounting and finance. Depending on what the property is, you may want professional advice on what records to keep to pay the least amount of tax when you sell.
