If iI read your post correctly your going to be setting up a small buisness that is fxing computers at the customers home ?
If this is your intent and your wanting to be able to connect a clients computer to your own service which will consist of your 4g cell phone and a netbook , you can either set your cell phone as a mobile hot spot or tethered modem. With the tethered modem option you can connect your phone to a router and then have your own private mobile network in which you can cannect a clients computer to for any downloads.
One of the best sources for information on just about anything is to do a Google Search.
For some really small routers for the mobile idea you can look at this web page.http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&DEPA=0&Order=BESTMATCH&N=100006654&isNodeId=1&Description=usb+router&x=0&y=0