+0
I say to the reception during check in:

Good thing there was a promotion on the hotel rooms, or else I wouldn't have been able to afford it.

Or

Good thing there was a promotion on the hotel rooms, or else I wouldn't be able to afford it.

Or

Good thing there was a promotion on the hotel rooms, or else I won't be able to afford it.

ARe all three okay
+0
Good thing there was a promotion on the hotel rooms, or else I won't be able to afford it.
This version sounds odd to me fora counter-factual situation.

Clive
+0
PreciousJonesGood thing there was a promotion on the hotel rooms, or else I wouldn't have been able to afford it.
I would say something more like this one.

Good thing there was a promotion on the hotel rooms, or else I couldn't have afforded one.

CJ
Students: Are you brave enough to let our tutors analyse your pronunciation?
Comments  
With 'good thing' as your introductory phrase, you can use any of those indiscriminately.
Mister MicawberWith 'good thing' as your introductory phrase, you can use any of those indiscriminately.
I don't understand why 'good thing' has so much grammatical power in a sentence...
It is casual, indicating that anything is liable to come out of the speaker's mouth next.
Site Hint: Check out our list of pronunciation videos.
 Clive's reply was promoted to an answer.
 CalifJim's reply was promoted to an answer.