This is real life advice, you honestly can't just "learn online" to do this, just read my threads and you'll see why, it's impossible. You can learn some things online such as how to setup the business and what's required like insurance etc but what you can't learn and what is possibly THE most important skill is buying correctly. It's not as simple as "just buy a car from auction at the right price". You need to spend hours searching for target cars, then you have to check them out including MOT history, pricing, HPI, condition, work required etc and after you've done that on say 10 cars you'll be lucky to buy one at auction with enough margin on it to make a profit worth the effort. This is why, in my opinion, if you're working at home selling a handful of cars it's just not worth the effort unless you absolutely love it, I believe you need a minimum of 8 to keep you ticking over minimising the risk of selling nothing in a month.
These questions might help you make a good decision:
Are you prepared to spend most of your day sourcing cars either Sat at your desk or at an auction full of sharks?
Will you have most of your day free without the distraction of kids at home?
Are you prepared to use your own family home for viewings? I've done it for 6 months and regret it, you only need one nut job and that's it, safety is compromised
Can you juggle your kids around to do home viewings professionally?
Are you prepared to clean your property for each viewing?
How will you do test drives if your wife is at work and you have the kid/s?
Are you prepared for the inevitable nosey dickhead neighbours giving you grief?
Are you going to use your own money or will you get funding?
How many cars do you plan on stocking?
What cars do you plan on stocking?
Do you have mechanical knowledge of cars?
What will you do with offering warranty?
What prep will you do yourself?
Do you have local contacts for Mot's, bodywork, repairs, tyres, parts etc?
Do you know of a location to take professional quality images?
Do you have a contingency plan incase you sell nothing in a month?
Have your researched advertising platforms?
Will you have a website?
Will you open multiple trade accounts to buy cars?
Do you have any competition locally?
Are you willing to work 7 days per week sacrificing family time for viewings?
Will you become FCA registered and offer finance?
Will you offer card payments for deposits?
Lots of questions I know only trying to help you make a sound decision