When you are interested in buying land for building, besides the location, price and legal condition of the property, you should take into account other factors. Even the most of them are a matter of common sense, and you probably have thought about them, it is always a good idea to evaluate them while seeking for the land.
1. Evaluating the slope inside the property.
If you have visited Costa Rica for a while, you have noted CR is plenty of hills, so, for lots of 1000 M2, or more, is usual to find little or even big slopes inside the property. Obviously, there are many flat properties, but many of them are not flat at all.
Study the property if there is an important slope (50% or more). If there is enough space inside, you could cut the dirt to have a flat surface for your home, creating small slope areas in one or more sides to avoid retaining walls, because those structures would increase the investment in your house (usually between 20% to 40%); if you do that way, it is necessary to leave at least the same distance far from the slope than how high it is, that is why the top high should be between 2 an 3 meters, being able to have the same distance from the slope, otherwise you should need retaining walls. Well, sometimes, using a good design, you can take advantage of the retaining wall: I did it for a client whose house was built in two levels, the main one upstairs, and the second, for the garage, laundry and guest room, using the retaining wall as part of the supporting structure of the level upstairs, saving some money by using the wall twice at the same time.
By the way, a flat propety shouldn´t be ideal, specially because of rain; if there is a tiny slope in the property to the road (5%), you are lucky because the rain would go out by itself or with a little help from you. If you have a flat property, well, it is very nice, but you have to see if the kind of soil could create little swamps or soft places that could be uncomfortable and, in certain conditions, dangerous (I am thinking about some places in Filadelfia, Guanacaste, with regular floods because of the rain, the river and the flat lands). Then, if you are interesed in a flat property, ask about how the water from the rain in draining in the properties around; maybe you would need internal drainages to collect the rain.
2. Location and facilities for public services and direct access. Some friends of mine bought a nice property, with a good price, several slopes to be honest, 1.0 km far from the main road, and now they are evaluating to invest more money for getting a comfortable access (in this moment neither a four wheels drive car can reach the property, only by walking).
So, even the price is important, distance from services and access should be considered. Otherwise, you could be investing as much as if you had bought a different property closer to services.
3. Considering wind and rain, even sun position.
Some people like open architectural forms for houses. So, it is necessary knowing the usual direction the wind blows and the rain comes, in order to prevent an uncomfortable situation.
For instance, I designed a house for a client with a little covered corridor in the entrance, but the customer decided (the owner is obviously the boss) to have just a sidewalk coming in front, in order to save some money. Well, in the first months of the rain season, when the wind and the rain went in the entrance position, he had a little flood in the living room and even in the dinning room and kitchen. In conclusion, he had to build an extra roof for avoiding the problem.
Talking about the sunlight, we have something pretty similar. Knowing the usual direction of the movement of the sun you can avoid extra heat, specially if your design is using huge windows.
Some people have talked here about air conditioning systems. In order to minimize that use, or even having no need of it at all, considering the previous factors is important. If you have enough windows to allow air crossig the rooms, using mosquitoes screens in windows even in doors, the place would be fresh. Having high walls (9 or 10 feet) would give you good space for the same purpose.
Then, using insulating materials between the roof and the ceilings will help you to have fresher conditions inside. I remodelled a house where all the bedrooms, upstairs, where like ovens; using a coat of an insulating material, pretty cheap, reduced the temperature around a 30% to 40%, giving a nice condition without extra systems.
4. Basic structural conditions of the ground.
Sometimes a lot could have problems about the ground´s capacity for holding the weight of a building. The Puriscal (1990) and Cinchona (2008) earthquakes are examples of damages because of soft terrains and places with landslides complications, specially if there are important slopes close to rivers or roads.
So, ask for usual problems there where the property is located. Otherwise, you should ask for a soil resistance test and then for an engineer or architect opinion about that. If not, you could have problems while building and later, and maybe you should have to invest more money to solve it.
Also, knowing the structural conditions would help your professional to decide the structural system that should be use to achieve a good balance between quality and costs.
In my opinion, building should give you more advantages than buying an already built house, because you can do it according to your likes and without selling charges (for instance, commisions), but one of the main factors that could complicate your investment is having no professional criteria for going ahead. Having a design would allow you to have accurate bids. Let´s remember materials are often a 60% of the whole house cost, so, chosing an appropriate design would save you money when you decide to build your project.