i would suggest a compromise. would it be possible to work this job half-time? then you could try before you buy, so to speak. see how being at home a lot and trading from home works for you. also, it would give you the opportunity to buy some time and see that your trading continues to be successful. i would also ask yourself the following: do you have what it takes to succeed in a bear market? how long have you been making the 250k at daytrading? if it's been at least 5 years, in both bull and bear markets, i'd say you may be ready to trade full-time. otherwise, not. despite this fact, however, i would still see if i could do the same job half-time with this company. most employers are pretty rigid, but sometimes they surprise you.
sorry, i hadn't read about the 18 months and the penny stocks. now that i have, i would say, wait at least another year. but still, if you are dead set on trading full-time from home, you might want to see if your employer would let you go part-time (two weeks on, two weeks off, for example).
According to this blogger, you should have about 20 times your salary saved up before you give up your day job. If you don't have that much, you should try to get a part time job to take the pressure off of your trading. http://quantinvestor.blogspot.com/2006/12/leaving-your-day-job.html