help me with cheap tape deck.

Have you thought of a DAT deck? I have one in my system and I use it for digital(CD) and the analog inputs for vinyl. I saw a used one on audioshopper for 200.00. You can purchase 2 hour DAT tapes for around 4.00 or cheaper. The tapes are small and easy to store. Good luck.

do you need DAC for DAT?

No you don't need an external dac for a DAT player. They are like one box cd players with a dac section built in. DAT players have a digital out to use a dac if desired.

See if you can find a Nakamichi LX5. If you wanted to spend the $$, a CR7A would be better (automatic biasing, alignable playback head, and a few other bells & whistles), but the LX5 is very good. It doesn't have analog VU's, but with cassette that's a benefit, not a detriment. VU's read average levels; what you have to be concerned with when dealing with cassette is peak levels, and the Nakamichi meters do that just great. I have both units, so I can attest to their quality as recorders.

i truly suggest a sony 3 head with dolby S!!!!!! $250 at frys electoronics (a warehouse sized store we have in california). combined with metal tape, it can be truly archival. the metal wont lose highs, and dolby s is ded (yes-DED) quiet clear accross the audio band, not just the top half. you cant tell if the cd or tape is playing! for that kind of money, you can afford to take the chance. btw, its NOT taking a chance.
nakamichi isnt making decks anymore and the parts are becoming scarce, in addition to people that know how to work on them, and i loved my 700!
....regards.....tr