Let's look at the most basic type of remote access: one stationary location to another stationary location. For example, from the small business owner's home to the small business owner's office.
Say hello to VPN, or Virtual Private Network. You can jump over and dive deeply into the Wikipedia entry, or let me explain what you need rather than reading about every underlying protocol.
At the least complicated level, you want a router at home to connect to a router at the office, negotiate some security settings for authentication, then become invisible, leaving a link between your two routers. Everything on your office network you have authority to see can be seen over the VPN. In essence, you've turned your two routers into tin cans and the data lines between them into a long, long piece of string.
The good thing about this basic setup is that it's secure over the Internet, because the link between the two routers is encrypted. Low end routers won't use military grade encryption, so someone could capture the traffic and spend the computing horsepower needed to break your encryption. That's as likely as gasoline being $1 per gallon by Labor Day.
The bad thing about this setup, like the hero's flaw in a Greek tragedy, is that one network can see the other network and vice versa, but that's all it can see. Your stationary router's VPN support is just that â€“ stationary. You can only connect to your office network from your home network.
For many situations, that's all you need. Even better, not accepting any client VPN connections, but only the one connection from the matched router on the other end, makes your office network considerably more secure, especially when using low end routers.
I said â€œmatched routerâ€ on purpose. It's much easier to setup this type of connection between two of the same routers, or at least routers from the same vendor. Even so, you may need support from the router vendor, your reseller, or a consultant to get things working properly.
Communications between your home computer and your office server(s) will be slower than in the office, because the connection speed will depend on the broadband connections between the two routers. But the speed will be usable more most jobs, especially those that don't transfer huge files or send tons of graphics from a server to your computer.