Greetings Thomas,
Your best solution for a low-cost scanner is the RTL-SDR dongle, and some scanning software.
The best one (currently) is the RTL-SDR.COM V3, ($23) which has a very good TCXO, software-switchable direct-sampling mode (for freq range DC- 25MHz), input protection (diodes), aluminum case, and SMA input. It will receive in bandwidths up to about 2.56MHz, and there is software that'll step it along, so you can cover a sweep from 25-1800MHz pretty fast.
The only down-side is that rtl-sdr dongles have no bandpass filtering and will show spurious signals, so you just need to keep its RF gain set low enough that they disappear. They are greatly improved with addition of notch filters for AM and FM broadcast bands (~$10-20 each).
For (free) software, SDR# ("SDR Sharp") is probably the most popular, with many plug-ins, including a full-featured scanner plug-in. There is also software that'll step it along and generate RF heat maps.
I'm not advertising for them, but I know what works... I use mine as a "poor man's" spectrum analyzer and freq counter, and after software calibration to a freq standard, it works quite well.
Don't get a cheap plastic DVR-B dongle; they have terrible oscillator that wanders around all over the place.
73, --kv5r
