I'd say its not worth the effort. Get something that you can grow into.
Besides, three gallons will not let you boil three gallons, at most, 2 gallons.
I'd say get at least a 7 gallon (28 qt) so that you can do a full boil with five gallons. (realistically you may want 8 gallons so that you have a little extra freeboard).
A guy on ebay has some 9 gallon ones that have a thermometer and a 1/2 inch dump valve for 99 dollars. he is out now, but will have more.
~"A fine beer may be judged with only one sip, but it's better to be thoroughly sure.
On Deck: Spruce APA, Chambord Fortified Chocolate Porter, Imperial IPA
Secondary: Belgian Dark Strong Ale
Kegged/Drinking: Cascade, Cent., Amarillo Pale Ale
Kegged/Drinking: Belgian Pale Ale (HG yeast for yeast cropping see above)