It goes totally against the grain mate !,the last thing you wanna do is ride something cheap on a track day !,spongy brakes,risk of blowing up & dumping oil everywhere !,knackered bearings dodgy mechanics who say they fettled it & havnt,apart from your own life,think of the the other 20+ in your group..
Having done on average 25/30 days a year up until recentley,here & in Spain/France etc,i can tell it gets very expansive,& thats if you dont have n off !.
Having said that,it depends how you wanna do them,i had the full kit,that a race team,genny,van awning,2 bikes bought new 08 R1’s,in full bsb Superstock trim,new rubber @ lunchtime !…with spares etc etc..
But,i’d still say save up & buy an ex race bike,or a nearly new something..
This is one sport to never ever cut corners on !!.