I quit my job last fall and moved onto a new job, on good terms with my previous boss and when we ended things I agreed to keep the door open and stay in contact in case he needed my help, of course this was with the understanding that it would be only if my time permits and I wanted to. 

I did do some small tasks for him after quitting, during the tail end of the year and beginning of this year.  I hadnt heard anything since around february so I thought that was that.  

He reached out to me today via text saying he might have some work next month asking if I'm interested and to give him a call. 

Im going to decline, would it be okay to send a text response? I dont see why a phone call is needed.  I was thinking of saying “Hi *name*.  Good to hear from you.  I’m so sorry but I’m taking classes right now for my current job on top of my work schedule so I don’t have the capacity to take on anything else at the moment.  Hope all is well with you and thank you for reaching out.” 

Would this be okay? I think its time to close the chapter though I do want to keep a good relationship.