KelZac,
Welcome to the forums first of, secondly, affordable or cheapest?
The cheapest, most basic DCC System is the Bachmann 44902 EZ-Command System, about $180.00
The best DCC System to start in (in my opinion) is the NCE Power Cab Complete DCC Starter System running around $199.00
To be 100% honest, any NCE Power Cab system would be your best choice for at least four reasons:
1. Affordability
2. Ease of Use
3. Expandable
4. Functionality
Add to that that there are more people on these forums (and most likely other forums) that use NCE equipment than the Bachmann gear. As such, you will have access to more people for advice and help in using setting up an NCE System, should you run int o problems.
There are other systems, Digitrax, MRC and so forth. Digitrax is very good BUT also complex. I can't talk about MRC as I know nothing about them. For what it is worth, I have a Digitrax System ($355.00) and now wish I had bought the NCE System. Actually, for $199.00 I am seriously considering buying one anyway.
Hope this helps.