I quit my job this year - not to play poker as a pro I hasten to add, but to work as a consultant doing professional assignments for agencies - the money per job isn't great but if I work like a horse I can earn the same in 6 months as I used to in a year of sitting in an office watching my soul die.
Before I did this I knew I had to prove to myself that I could do it because I'm quite a risk-averse person but also I know how important it is to believe in myself.
So I went part-time at work and did agency assignments alongside my usual day job. I kept track of my cashflow and how long I spent working for the money so that I could analyse my earnings.
Once I suspected it to be possible, I booked two weeks off work and just acted like I had already quit; I threw myself into the new task like my livelihood depended on it and took as many bookings as I could.
Finally, I went to that person I trust who knows me better than anyone else and explained everything, answering every question and finally ask them whether they think you can do it. Belief in yourself is great but you need reassurance too and although they won't know the ins and outs of your venture as well as you do, they'll know you well enough to understand whether you believe what you're telling them or are just deluding yourself. Think hard about who to ask - who do you trust to be objective?
Once I'd already decided to leave my local govt. job and started telling my plans to people there almost every one was sceptical along the lines of "what if it goes wrong" or simply "you get paid every month here why would you leave that".
What if it does go wrong? Have a plan C, and a plan D...
And as for their other comment - you only have one go at life on earth. I really want to spend 50% of my waking time at a desk in a stinking office to be able to retire once I'm too damn old to enjoy it properly?
Your position seems very similar - you think your plan might work for you and have an opportunity to try it out without taking the ultimate plunge. So try it, but you have to act like it's the only chance you'll ever get and give it 100% or you can't really know if it will work out.
Try it. Do the same things. Analyse your income and see whether it's possible to win enough per hour on average to both bring in your current salary AND grow your bankroll or are there simply not enough hours in the day.
If the figures still say to you that it is possible then trial it for as long as you need to to prove it to yourself one way or another - and do it safely with the monthly living expenses already in another account and a way back in to your job if you need to go back (plan C). Be utterly honest with yourself, because you don't want to be explaining your plan to the bailiff as he empties your flat in a year's time.
A lot of people will tell you that you can't do it and you're the only one who can tell you for certain that you CAN.
I've waffled a lot, sorry.
One last point - Don't ignore all the advice out there on BRM.
If a pro is meant to have a BR of 100x BI, $700 has you playing $5 poker by my reckoning or maybe lower (I'm not a poker pro!) . How many BB do you have to earn in every hour to cover your expenses and grow the BR?
Is this level feasible? - if you don't know then you need to be asking that question... if it isn't then you're only giving yourself the opportunity to fail - can you wait, grow the BR and give yourself the chance to succeed?