(?) my salary is not big enough to cater (to? for?) restaurants.

Grumbler, "cater" means to provide food and drinks for parties and formal events.

"State Benefits do not cater for luxuries - nor do they enable a serious drug habit to be financed." - http://www.telegraph.co.uk/comment/personal-view/3635223/Drugs-are-the-curse-of-our-land-and-turn-women-into-prostitutes.html
"With the high sources of revenue to cater for the increasing budget expenditures in most of the countries, ..." - http://world-tourism-articles.blogspot.co.uk/2015/01/attraction-management-analysis-of.html

I do understand that combined with restaurants it sounds ambiguously.

Yes, I was thinking of food

But even then, it's not used that way talking about oneself and one's finances.

That's why it was in comments and with question marks.
How about "...extra R7000 will assist rapidly with petrol, airtime, braai back, restaurant dining and all the other small things your salary doesn't cater for"? The currency implies that this can be not native English.

Yeah, it doesn't sound too good. I don't recommend it.

OK, thank you

You got it.