There are some great deals on lots at the moment, so now may be a good time to buy. However, make sure you do your homework before purchasing the lot. Utilities, soils, slope, deed restrictions, length of utility runs and length of driveways all need to be considered. Each of these can impact costs.
Living in town is great because you have utility services, and a shorter commute. You will need to pay tap fees, which tend to be less than a septic or well, and site costs can be lower because of shorter driveways and shorter utility runs. Some costs to consider are added survey/inspection costs and architectural fees in the City of Austin McMansion areas. The city requires a tent envelope be drawn for approval, then a survey done during construction to measure the height to make sure the house is within the drawn envelope. This can add several thousand dollars to your project.
Lots in the country tend to be larger, giving you more room to enjoy. However, you need to find out if water and sewer is available. If they are available, how much will the tap fees be? Also, how long will the utility runs be from the tap to the house? Digging long runs can get expensive. If utilities are not available, what are septics running in the area? Water can be provided by wells, depending on the aquifer, or by rain water harvesting. Each of these can add to your costs, so make sure it is figured in.
Deed restrictions are also important. They can help make sure the surrounding homes are similar in construction so someone does not build a shack next to you. They can also add to the costs if more expensive roofs or other materials are required. Just make sure you know what they are to adequately include them in your budget.
A building expert can look at a lot with you to help you think it through. They can see if there are issues with slopes, utilities, access, or other considerations. That way you can be educated before you purchase the lot.