kind of formalities we need to do to start rent Business

Consider the type of rental operation you’ll run. The two main types are contract hire (where customers - typically businesses, lease vehicles for a set time), or daily hire (where customers – typically individuals, hire vehicles for a shorter period of time).          INSURANCE:  it’s illegal to trade without some form of fleet insurance. It’s worth shopping around to find adequate cover at the best price. Besides the formalities of starting any business, a rental business has extra insurance liabilities. Your entire business depends on non-employees interacting with your equipment.

So while you want to make sure you have good insurance for your equipment, your customers are your biggest risk. Even with no-liability waivers, make sure you have the right insurance.
make your customers aware about how should the rental equipment be treated – what is acceptable wear and tear?
When and where does the rental end and start?
What should the customer do if something goes wrong?
What are the penalties for damage, loss, theft, late returns, …?