Free Digital Audio Workstation (DAW) like Garage Band for Mac - Free

Music Production Keyboard - $120 (link to one of the best to start with in my opinion)

Basic digital audio interface - $40

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$160 plus cables, monitors/headphones and other misc. and youve got your basics to create and produce all the songs in your head youcould want. As you progress, youll want higher end equipment but thats a pretty great set up to start with.