Where you live, your record, so many other factors influence your premium. You really have to call to get a definite answer but brace yourself for $2,000-$3,000 a year for a 250cc. I started on a 250cc bike but was much older than you so my premium was half decent.
For commuting a 125cc can do a highway, just won't have much acceleration on it to pass or go up a hill. That thing is super economic though. I think around 3l/100km.
So, bottom line, if you're thinking about saving money - calculate exactly how much you spend on gas and remember that you won't be riding the bike in heavy rain, winter or when you need to carry loads, so you will only save occasionally. So if your gas bill is $3,000 a year on the truck, you will save about $1,000 by riding the bike half the time (assuming the bike will burn around 1/3-1/4 of what the truck does). Plus extra maintenance cost, tires, gear and such. So the actual savings would be even less. Maybe $500. That won't offset the cost of insurance.