First you need a small but powerful computer:
Don't let the manufacturers scare you into a larger and more expensive computer than you need. I have an HP Netbook with 1 GB of Ram and a 160 GB hard drive. It's not blazing fast, but certainly fast enough. It weighs in at just a couple of pounds, and has a 10.1 inch screen, and a 92% size keyboard compared to a regular notebook. I have video and image editing software installed, and it works just fine. I do all of my business, both real estate and writing on it.
Now there's the printer - one you probably haven't seen:
Though I also have an HP 460 series portable printer, I never really carried it around. It was still too large for just having around town for contracts. I would carry it on trips, as I could pack it in my larger suitcase and check it through. Now I have a Pentax PocketJet3 thermal printer with roll perforated 8.5" x 11" paper. The printer itself is only 2" x 10" x 1" and doesn't use ink. Even with the paper roll accessory, the entire thing is about 3" x 10" x 6". A great battery and bluetooth make it a completely wireless solution with my netbook.
The bag it all lives in:
I had purchased a small Targus bag for the netbook and accessories, but was very surprised to find that the printer fit in one compartment and the computer in the other. Altogether, the exterior dimensions of the bag with the printer and computer inside is 11" x 4.5" x 8.25." So the peripheral accessories and cables get thrown into another small bag, as I don't need them for most of my mobile contract work, with batteries taking the place of the charger. The extra high capacity battery for the computer even fits in with the computer and printer.
Now, with just about everything I'm doing as an online service, there's nothing I can't do on the hood of my car if necessary. I use online email, CRM (customer relationship management) software, screen capture to video online, images and image editing online at Flickr, etc. I'm using a Verizon MyFi cellular broadband modem that allows up to five computers to connect for high speed access anywhere I have cell service.
Last Saturday, I met a customer at a condo project to look at several units. He decided to make an offer on one. It was staged, so we just sat down at the dining table in the unit. I pulled up my online ZipForm contracts, filled in the purchase agreement, printed it, got it signed, and then scanned it into the computer when I got home. I could have used my Docusign "sign in person" option to have digital signatures, and I wouldn't have even needed to print it except to hand the customer a copy, which I emailed anyway. I emailed it to the listing broker's office, and went out to dinner.
You just have to love technology!