Quickly create a landing page using something like Unbounce then drive some traffic to it ie. spend $100 on AdWords.
Offer something like free access to your product or service for the 1st 100 signups. If you get traction, you'll know you've got something. Then you can use those initial signups as a beta group.
I'm in a startup accelerator, and I can attest validation is one of the most important components they drill into us. Do whatever you can get in front of people and at the very least get people to say 'yes I want to use your platform', the more passionate the better, but even better than that is get signed contracts/deals before launch, or people who are passionate or excited about your app.
Go to Meetups in your local area & listen to the things that people complain about & create a list. You'll find out that people usually complain about the same things.
Before you dive in & do consulting full time, make sure you have a few PAYING customers. The biggest issue with consulting is the recurring revenue issue. You want to have paying customers already then get referrals from them to keep business coming in.
Well as revenue is largely from ads (that are reliant on page views) I needed to build up visitor numbers to generate ~100k page views a month on a regular basis
Each visitor brings about 2 page views on average so 50k visits a month puts me over the threshold. Uniques are at about 70% (I'll leave that as an exercise for the reader)
But to actually turn a profit... I really only need a very small fraction of this. Maybe 10%..?
It's all moot tho, as I need the numbers to be high as this is what gets advertisers paying. Thankfully this comes with a natural abundance of funds making this the most profitable project I've ever worked on