I do parttime videography
Then forget standard definition altogether and tape-based recording. Of course it's going to be highly budget-dependant.
These days, if you're getting paid to do some semi-professional work for someone you want your recording to be at bare minimum 720P (even if you plan on exporting out to DVD for the final piece). Full HD is the standard (1080p) although many professionals now shoot in 4K for their masters and exporting out to Blu-ray or H.264 files.
I do a bit of professional work for theatre productions in my spare time (recording promos and things like that). I started off using the
Sony HXR-NX5P which did the job pretty well although it's now a discontinued model. It was fairly flexible for the price (I think I paid about $7000 for the entire kit with some extras). I bought the add-on 128GB external solid state recorder, but it also had 2x SD card slots for recording (when one became full it automatically switched to slot 2 and you could remove the first card on the fly). The
Sony HXR-NX5R replaced my old camera.
That was about 5-6 years ago now. These days we use the
Sony PXW-FS7 cameras (it does 3840x2160 @ 59.94P, very nice) and record straight out the SDI port to external recorders to an uncompressed format. The built-in recorder is only used as a backup in case something fails. I should point out, Sony professional cameras have excellent battery life. I think with the larger battery, I was getting something like 5-6 hours recording time out of a single charge.
If you have a few grand to spend, I strongly recommend you check out
Sony's NXCAM and AVCHD camera range. They offer good bang-for-buck with a lot of advanced features (you won't get everything in one unit unless you pay big money).
If your budget is even less, the next step down would be one of the Canon or Nikon DSLR cameras which also shoot HD or 4K video. You can get very good results with them.
Your audio is just as important as your picture so don't neglect that. There is nothing worse than watching a stunning HD video with crap, echo-ey audio. As you probably already know, it can become an expensive hobby.