Here's my recommendation.

1. Get a refurbished iMac, or if you need pretability, a refurbished MacBook.

2. Add a small mixer than can accept as many mikes as you will want to record at once (two for solo voice&guitar) and consult with an audio guuy to learn which mike will serve you best.

3. Download SoundStudio, a free trial version, and start recording. You can export to AIFF, WAV, MP3, etc and apply all the filters you could want in a simple, easy-to-understand interface.

GarageBand is also a phenomenal program for these purposes.

A