If you have little to no experience buffing the porter cable 7424xp is tough to beat. It is a very forgiving buffer to use for first timers and has respectable correcting power. The OP has probably bought by now, but the information below will be great for those who read in the future. Three things that have not been mentioned so far are: 1. Cable length 2. Pads and 3. Prep.
1. Cable length: Many buffers come with cables that are too short and most people grab a spare extension cord collecting dust in the garage. If your gauge and ampere rating aren't right for the desired length than you can cause damage to your buffer.
2. Pads: How many you need depends on how big your vehicle is, its conditions, how much work you plan to do in a day as well as the type of work (heavy correcting, light correcting, finishing). Ideally you would want 6 compounding pads (deeper scratches, deeper swirl marks), 4 polishing pads (light swirl and maring) and 2 finishing pads (gloss and protect) per vehicle a day. Understand that wherever you are buying less is where you will be handicapped in how far you can go in a day.
3. Prep: Not doing a decontamination wash ( normal car cleaning, but adding in a fall out/Iron Spray and claying) is just not smart. This removes contaminants from your body work so you don't introduce heavy marring to your paint.
What you need:
-Porter Cable 7424XP
-Lake Country 6 in backing plate.
-Lake Country CCS pads 6.5in: CCS pads do a good job with heat and that is important with buffing. Ideally you would want 6 compounding (any combination of yellow and orange, 4 polishing (white), 2 finishing pads (black). You can get by with this if you want to save a little and expand later: 4-5 compound pads (3 yellow 2 orange) 3 polishing (white pads) and 1 finishing (black pads).
-Snappy cleaner packets: Stupid cheap and make cleaning pads a lot easier
-M105 compound M205 finishing polish.
-Snag some microfiber buffing towels if you don't have some already
-Automotive tape
-Fall out/Iron spray
-Clay: Nanoskin fine grade mitts save a boat-load of time by hand.
The above setup will treat you very well for years to come, create fantastic results and you will build confidence very quickly in your abilities. Not only this, but should you decide to upgrade to something more robust in the future this setup can be interchangeable with the Flex 3401 VRG in the sense of same pads, polishes and similar technique.
Other things to consider that you may want to invest in:
-Lake Country 3 in backing plate: You can change the backing plate to a variety of sizes to make working in tight areas easier and more effective than just 6.5 in pads.
-Lake Country CCS pads 3.5in: 3 correcting (1 yellow 2 orange) 2 polishing (2 white) 1 finishing (1 black).
-Sun light buffing: Buffing in the sun can be done, but it isn't ideal to say the least. Heat and paint correcting usually is a bad idea for a variety of reasons. If you lack a home garage to do the work in then moving to a shaded area or more ideally a cheap pop-up canopy is wise.
-Lighting- Working in a home garage, it can be pretty common to lack the lighting needed. Lighting is important in saving you time as well as making paint correcting easier. Scangrip tends to offer top quality lighting options, but they are expensive. For those on a budget consider getting a bright LED fixture that screws into a light bulb socket in your garage from overhead, a bright head lamp or something like a porter cable LED light that you can stand up behind you while you work are all sub $50 options.
-Wheel cart: Not a need, but really nice when you are buffing for hours. Saves your knees and back a lot, it also provides a useful place to put your buffer when not buffing, product, spare pads and even your buffing towels while you work.
Sorry for the length, but buying a buffer is initially expensive to a certain degree with many variables to consider.