how create VPS resller company..?
What is needed for that?

You get a VPS Control Panel that allows you to create VPS Resellers and a Dedicated Server to put the VPS Control Panel on it.

Seeing the trend of shared hosting business, I think a lot of serious web site owners will be migrating to VPS, so setting up a VPS service is always a good idea.

You need to do your research first before opening a VPS service, one thing you should know well is to support your VPS clients when things goes wrong.

Going into the VPS business is entirely different from shared hosting, your technical skills must be well tuned so that you can support the VPS customers properly.

Seeing the trend of shared hosting business, I think a lot of serious web site owners will be migrating to VPS, so setting up a VPS service is always a good idea.

So, what's this trend of shared hosting business you're referring to?

You need to buy dedicated in order to sell VPS

I'd agree with the above advice, you'll want to do your research. You can never have too much information.

Also, make sure you have a solid business plan. Make a plan and adhere to it. Outline your goals, policies, and procedures.

Make sure your systems and configurations work properly *before* selling them. Stress test your servers if possible -- know their limits. Know how they will function under load. If possible, know the parts you put in your servers, and if they have any known quirks (no hardware or software is perfect).

Know the limits of your technicians and colleagues. Each person on a team should be aware of their team's strengths and weaknesses. Understand that people aren't perfect, but know where your holes are and work to cover them.

Know your market. Find your niche and work to improve it. Dont rush expansion, but don't sit by the wayside and let your competition win, either. First out of the gate does not always win -- the person in last place never wins.

That's the best advice I can give. Be serious about this -- the industry has a lot of fly-by-night companies as it is. If you seek success, be ready to make this your life.

how create VPS resller company..?
What is needed for that?

Technical ability, vision, and a sound business plan. None of which can be obtained on an internet forum.

what if it wants to build a reseller VPS, by using the VPS as well. Equipment and software in what should be provided to support all that?

You only need the technical knowledge to configure your node. Its your choice if you want to offer managed or unmanaged vps.

You can not create VPS with VPS.