If I understand correctly you are wanting to home host on a bought machine rather than pay monthly as you are now for shared hosting? If this is what you are looking to do, then I would highly discourage it as home hosting a public server can lead to multiple problems.
Firstly regarding costs, buying a suitable dedicated machine to run 3 servers on will cost more than $750. And that is without taking into consideration the costs of powering this machine 24/7, and your ISP internet fees.
Secondly regarding more serious issues, running a server from home can lead to serve security issues as you can easily get attacked by DDOSers, which will take down the internet for your whole house. Your ISP (Internet service provider) most likely also does not regard game server hosting as normal use, and therefore you can end up with heavy fees for running such a server from your home, and even get your internet cut off. All in all, costing you more money, and resulting in server down time for your players. On top of this, you will be putting heavy strains on your power, which can also cause short circuits, resulting in server down time, and possibly damaging your actual machine. You also have to realize that your ISP will not provide fast enough internet for you to host a server, which will also result in a laggy server for your players.
So overall, home hosting a public server is not a good idea. You will not save any money and it can cause a lot of problems for both yourself and your house hold. Instead I suggest you look into renting a dedicated machine or multiple VPS from OVH. They offer very low prices for some great specs and if you have the technical knowledge to set them up right you can fit hundreds and thousands of players on their machines. Take a look at their ranges and see what best fits your budget and needs:
http://www.ovh.co.uk/
