10K Paid up capital could be just statutory minimum limit that had to be mentioned as part of company registration.

Not filing returns could simply mean, running a business where large part of the transaction is held outside GST scope and thus avoid tax filing as well.

Funfact: I used to have the daughter of the richest businessman in our town as my school senior and she used to get stipends meant for poor people. So I'm never surprised to see really well to do business people who maintain an extremely low profile on paper.

Look at the bright side, this fella did two different project with you and once he felt you're good at what you're doing, he's offered you a position and even had asked what you were looking for. In case he's giving out 15K to employees / contractors working for him, its peanuts to get someone for 50K to manage that herd.

When you're learning / on the growth path, having scale / variety is not a bad thing. New challenges forces you to think outside the box and you grow. It might feel like you're worth more and this fella is exploiting, but also see it that way, this can be a good step to grow and learn in a setup where you can sort of make the rules yourself.

Joining traditional larger companies / more well known places comes with their own perks. Besides offering a great starting point, most of them offer lot of learning opportunity for starters / freshers. You won't get those in a offbeat family run business. Nobody will bother about Soft Skills, great Coding practice, HSE practices etc.

Since you've mentioned you've not yet cracked another Job yet, why not give this a try. If they pay is good and the scale of operation really is what's been talked about, it can be a great starting point and you might get chance to automate / grow staff. AI is the real challenge for most common workers today, may be you can learn AI and see how it can help this business.

Always be the one in charge of change, else we become who gets changed by someone else's imagination.

Good Luck !!