Web based Project management tool

I am planning on starting a Web based PM business to cater to small manufacturing plants. I know there is a small market for it and I want to use it. What are my best options:

1. Have someone create a Web based software like ManyMoon, SmartSheet, Gantter project, Zoho project
2. Or buy enough licenses from the above and customize and market

I am not sure which option to take or what other options are available. Your answers are greatly appreciated.
Thanks

There is another option, which would be to find some open source project management software and install it on your own server, then customize for your needs. Also, check out these guys I just started working with yoxel.com - they write interface programs for various online PM programs including Zoho, and they just developed a personal task manager that interfaces with Google Tasks.

I like your business idea, by the way.

Yeah find a good open source solution and customize it.

We kind of do this with www.redmine.org it's a great PM system, and very customizable.

Really isn't a reason to start from scratch. Redmine is built on Ruby on Rails so you could build 'plugins' for any specific things to your industry or market.