Viral News Boy :- It is possible to make your own Wi-Fi software.It would be far cheaper to purchase a Wi-Fi router than try to build one from the scratch.For the software alot of programming knowledge is necessary.Alternatively if you want a Wi-Fi that is set to your own preferred standards on users devices then look at the wetinBe IBE player.This player gives wifi on demand and the user access may be restricted as you may require.Internet connection is not required for the wetinBe IBE player to work.
WiFi requires a radio transmitter and generally those have to be type approved, unless you have a radio amateur license.
Hardware, software or just having your own Wi-Fi network,I believe there are a number of Steps and open source router or access point projects available out there.Grab one and figure out what you want to do with it.
It should be noted that most of the Wi-Fi chips ets can be smoked by trying to run too much power through them, so this is a case where a software bug can cause hardware damage.
If you just want to make your own Wi-Fi network,all you need is a router or access point device, with some little amount of money to buy necessary requirements.You do not need an internet connection to make one of these work, but you will quickly discover that everything with a WiFi chip in it assumes the availability of the internet.