The number of users you anticipate having is a very important aspect of install a wireless or wired network. This is not how many people this revolves more around the number of devices. If you anticipate having 5 devices then you do not need to break the bank. However this applies to more users as well. If you anticipate having 100 devices then purchasing a consumer router from Staples may not be the best plan of attack.
Understanding how many devices will be on the network allows us to suggest the best equipment for the number of devices you will hold on your netowrk.
What do I mean when I say, "Incoming Speed". Although you do not need to know alot about this I am going to give you a basic understanding. Your ISP which is your Internet Service Provider, give you a speed. This could be 50Mbps, 100Mbps, 200Mbps, or even 1Gbps (Mbps = Megabits Per Second, Gbps = Gigabits Per Second). Your ISP could be Comcast/Xfinity, Verizon Fios, Direct TV, Dish, etc.
Your incoming speed needs to be able to withstand the number of devices your network is going to support. If you only have 3Mbps as an incoming speed and anticipate 100 users then you will need to increase your speed by 200%. This will increase your monthly bill from the company.
Now when I ask this question you might be confused becasue I am not a Genreal Contractor. However this in my opinion the most difficult and important step of them all. When I ask how many square feet I am more concerned about how much of you space you would like the wireless network to cover. However covering your entire space would not be a bad idea.
The reason I say this is because any wireless signal slowly fades out. Which means if the signal only goes just to the edge of your space then you will not have a good signal in many parts.
When it comes to reliability there is a lot that can be done. In other words you can go as cheap or as expensive as you would like. However, wireless technology is a product where you get what you pay for. If you buy a comsumer level product then you are not going to get the best possible reliability.
I personally suggest Entry Level Enterprise equipment. The reason I suggest this is for three reasons. Reliable, Wallet Friendly, and Easy to use. One of the companies that I believe fits all of these characteristics is Ubiquiti. Their technology can compete with many other Enterprise companies and also does not break the bank.