You need to get clear on the 'why'. What is the purpose of you wanting an online business? When you've got your first answer, ask 'why' again, and then ask it again. Asking the '3 whys' really gets you to the nub of why you want or need something.
Tip: It really helps to have a burning 'passion' for why you need an online business. Without it, the inevitable headaches, hassles and heartache could lead you to give up, accept defeat and say, 'It's just not worth it'. Find a reason that matters deeply to you.

You need to build a team around you that will support your vision, provide expertise you don't have and hold you accountable. A basic contractor team includes:

You also need people to hold you accountable to completing. Either commit yourself financially to the project so that there's no backing out, or commit yourself emotionally (to your clients, or in a public statement) to ensure that you step up and make it happen.

You need to be confident in what you're selling: that it has a market, that the prototypes work and that testing has been conducted using a Minimal Viable Product (MVP) that real people have paid real money for.

You need to know that what you're offering has a target market that's able and willing to pay your price, that the demand for what you offer is in a growth phase, that you're not differentiated by being the lowest priced and that it is difficult for others to easily replicate what you do.

You need to demonstrate credibility, provide third-party proof that you are as good as you say, answer every question the customer has about the product (before they buy it), make it easy for them to buy, offer an iron-clad money-back guarantee and prove that you are a real business with real premises.

You need to have an online identity that reflects who you want to be and how you want to be seen, great content that operates 24/7 selling your business while you can't and a website that ranks well on Google.

You need to be able to market your business using PR, print, social media, events, email and content marketing and a raft of free resources to offer in exchange for the prospects' contact details.