Buying a classic motorcycle doesn't have to cost the average tax refund (currently $3036). There are many inexpensive motorcycles that are considered classics which are perfectly acceptable as daily rides too. The good news is that most, with regular maintenance, will hold their value. Realistically, the less collectable a bike is, the less it will cost. Bottom line? A great looking bike can be had for less than $3000.
Some typical examples can be found with older Japanese machines. For instance, a 1978 Yamaha RD400 in fair condition can be found regularly on sites like eBay for less than $1000. Another Yamaha that has been very popular over the years is the XS1100.
A 1979 XS1100 can be bought in good shape for around $2000.
Kawasaki KZ900s (similar to the one in the photograph) are also worth considering. These bikes had very strong reliable engines (I used one in a racing sidecar) and a clean example from 1976 can be found for around $2300.