Is it to be a love match or something more . . .

... mercenary.

Please do not use mercurial when you mean mercenary.  Mercurial does not mean mercenary.  

Mercurial — “characterized by rapid and unpredictable changeableness of mood” (Well, there is also the "thievishness" thing, but is marrying for money quite the same as being a thief?)

Mercenary — “serving merely for pay or sordid advantage; greedy”

Marrying solely for money or position is mercenary.  Unless the heroine/hero is also changing their mind about it every few seconds, it is not mercurial.

As well, I would ask you not to use either "mercurial" or "mercenary" eight times in ten pages. 

As a romance reader, I thank you for your consideration.