Aertael is a large and diverse city. It long ago outgrew the curtain walls built to protect the city many years ago, and the area outside the walls has farms, ranches, a large necropolis, a fairgrounds, and a great deal of residential area. Not much business, other than those listed above, exists outside the city walls, as population density is too low to support most.
Inside the walls, the city is informally divided into four districts, mostly by tradition and related property costs.
The southeast side of the city consists mostly of large warehouses and light industry, and the residences and support businesses for those who work in such. Most of the poor of the city live here, and thus, much of the small crime. This keeps property costs low.
The southwest side of the city is more middle class, with businesses more on the retail side and less on storage and industry. Most of what would be considered 'shopping' is in this part of town, and the bulk of the population lives here.
The northeast side of the city is where all the temples are, and most government offices, including the royal palace. Upper-end business are generally found here. There are some residences, but not a lot, as property is fairly expensive and the presence of government and military structures make this part of town busy and noisy.
The northwest side of town is the upper class side, with larger and more expensive structures. Most of the businesses that exist here are high-end retail, fine dining, pricey hotels, and the like. Inside this part of the city is an enclosed enclave known as the Emerald Estates, where property is very expensive, seldom comes up for sale, and is generally owned by the old families, and/or noble members of society.
There is no unused space of any real size inside the city walls, so those wishing to find a business location or home inside the walls must either buy or rent an existing structure, or buy one and tear down and rebuild.
Cost to buy property in various parts of the city, and outside it. Note this is a general guide.
Notes:
1. The southeast side of town, outside the walls, is adjacent to a necropolis; prices are lower as you get closer to it. This is also true as you get closer to the farms.
2. The southwest side of town is adjacent to farms on the south side, and prices are lower there.
3. The northwest side of town is mostly ranches, and few want to live there, so prices are very low.
Buying or building structures
There are two ways to go about this, if building. You may use the construction section in the Dungeon Master's Guide; this requires a good bit of detail, and even after, you will wish to estimate costs for furnishings and extras such as grounds. A simpler way is to think of a home or business that is similar to what you have in mind, find out the real world cost, and divide it by five to come up with a gold piece cost (thus, a million dollar home would cost 200,000 gold). I am fine with either way; if you do detailed information and drawings, you will be rewarded with character improvement points.