Honestly with a PC600 you are going to be very limitted in what you can do and your not going to be able to compete with the cost of the people with inkjet printers. With my inkjet printer I can print for about 35 centes a sq foot (Both vinyl and ink), I believe the PC-600 is about $2.50 a sq foot.
The PC-600 can not do larger prints without banding (from what I understand). About 4-5 of my wholsale customers have PC-600's and they still outsource prints to me because its just easier and cheaper for them.
Also PC-600's are known to blow heads quite frequently, and they are not cheap to replace.
Oh and Yes you can print on trasnfers with inkjet, just like you can with the PC-600...
As for getting into an inkjet used, your probably looking at atleast $7,000-$10,000 for a 30" Versacamm or Small Mutoh. I dont think you will really find anything cheaper than that unless you get REALLY lucky.