OK, I'm not really sure if the following information warrants an answer or should be added as an edit to a question, but here it goes:
After extensive googling I think I found the original quote. It was given in a Polish newspaper, by a Polish philosopher Marcin Król - and my memory did not save me very well, as the exact quote did not come from de Tocqueville itself, but from the wife of Marcin Król :). The passage, loosely translated from Polish to English, reads as follows:
University [...] does not teach a given profession. It teaches to think. However, [...] in order to achieve that, it needs able lecturers who do not pursue money, but gracefully share knowledge and intelligence. Tocqueville knew that to think one has to have abilities, free time and money. My wife used the following wise words to express the same idea: to be a good humanist, one has to own a folwark.
So, while - according to the original author of the article de Tocqueville did not give the original quote on having a farm, he did indeed stress the need to have money and time. I'm not sure though, if Marcin Król's summary of de Tocqueville thought was very accurate and did not serve mostly as rhetorical instrument. Consider, for example, this passage from de Tocqueville:
If the democratic principle does not, on the one hand, induce men to cultivate science for its own sake, on the other it enormously increases the number of those who do cultivate it. Nor is it credible that among so great a multitude a speculative genius should not from time to time arise inflamed by the love of truth alone. Such a one, we may be sure, would dive into the deepest mysteries of nature, whatever the spirit of his country and his age. He requires no assistance in his course; it is enough that he is not checked in it. All that I mean to say is this: permanent inequality of conditions leads men to confine themselves to the arrogant and sterile research for abstract truths, while the social condition and the institutions of democracy prepare them to seek the immediate and useful practical results of the sciences
In my opinion it states the opposite: democracy is a good ground for thinkers, who - in place of great overreaching theories - aspire to discover immediately useful truths. De Tocqueville goes even as far as to say in the title of one of chapters of his book that "The Example Of The Americans Does Not Prove That A Democratic People Can Have No Aptitude And No Taste For Science, Literature, Or Art". On the other hand, there are passages that connect wealth with intellectual endeavours:
The wealthy will not be so closely linked to one another as the members of the former aristocratic class of society; their inclinations will be different, and they will scarcely ever enjoy leisure as secure or complete; but they will be far more numerous than those who belonged to that class of society could ever be. These persons will not be strictly confined to the cares of practical life, and they will still be able, though in different degrees, to indulge in the pursuits and pleasures of the intellect
I must say I feel a little embarassed, as I didn't remember the quote well and it came from rather obscure source. I have already upvoted this answer, as pointing in the good direction.