First, let’s consider if it is indeed possible to make gambling a primary source of income.
And how much are you willing to invest in it? Let's be clear, you can't make money without money. So if you want gambling to be your main source of income, you need to have a very nice bankroll, big enough to withstand some bumps... and even pro players who play for big money have their bad days.
The specific question is how much money someone wants to make on a weekly/monthly basis... if we take for example someone who wants to earn $1000-$2000 from sports betting and poker what would be a desirable starting bankroll? $10k-$20k or more?