Let's look at that part of the paragraph in detail: it's worth it, because the subject of money( and the lack of it) is crucial to this story, IMHO.

In fact, these opening paragraphs show how very unfair the law relating to estates could be ,particulary to the women of a family : but it also exhibits quite starkly that those who owned such estates had an awful lot of free will.It was they who chose how their property would devolve, and sudden caprices could have far reaching and serious consequences.

The owner of this estate was a single man, who lived to a very advanced age, and who for many years of his life had a constant companion and housekeeper in his sister. But her death, which happened ten years before his own, produced a great alteration in his home; for to supply her loss, he invited and received into his house the family of his nephew, Mr. Henry Dashwood, the legal inheritor of the Norland estate, and the person to whom he intended to bequeath it.

The phrase "legal inheritor" meant that Mr Henry Dashwood was the legal heir to the property under the opeation of the intestacy laws.

These laws came into operation if a person died without leaving a will.

Therefore, if the "Old Gentleman" had not left a will to the contrary, the estate would have been Henry Dashwood's and all family would have been financially secure for the furture .

Sadly for Mr Dashwood, though he inherited the estate, he was only given a life tenacy,as Maisy pointed out. He was in a similar situation to Mr Bennet in P+P. Not being the "ultimate " owner he was therefore restricted as to what he could do with the property to help his wife and daughters.

And there could be no attempts by Mr Dashwood to break the entail( which is the term for the clause in this will which related to the inheritance of the Norland estate) until young Harry , hish grandson was of age, he being the residuary heir under the Old Gentleman's will.

Mr Dashwood therefore resolves to save money from his income from the estate, in order to provide for his second wife and therir daughters( an attitude quite unlike Mr Bennet's short sighted view in P+P,don't you agree?).Sadly his laudable attempt to this is cut short by his premature death, thus ensuring that the Dashwood ladies are not particlarly wealthy at all.

Does that help?