comma before 'and then' [conjunction]: loan is $100, and then there

[avbm]

"And then" can mean "in addition" or "next".

Is it true that when it means "in addition" you must always put a comma in front of it? For example:

"The loan is $100, and then there is the interest to pay."

 

[Starfrown]

I think you're pretty much right, but in many cases, a dash is appropriate.

"The loan [itself] is $100--and then there is the interest to pay."

There is very often a strong pause before a phrase introduced with "and then."