Re: Hi, looking for some advice :-)
If you're going to get a cheap cruiser brand new, do yourself a favor and shop for one that has front and rear vbrakes instead of just a coaster. You'll have less hassle with installing the sprocket, and you'll have decent brakes.
As mentioned, craigslist is also good for finding a platform used. Don't forget Goodwill, Salvation Army, or your local police auctions.