By real estate I mean the amount of available attention. It could be conceived of as time, space, or energy, too, but for now let's use the idea of attention, what the mind can attend to at any given time, or on any given day.
A big project you are working on occupies a lot of it, and it does so even if you are not working on it very much. A course you are teaching occupies a certain amount of real estate, even during the hours one is not teaching it or preparing it. We talk about a teaching "load" as though we are trucks and have a burden to carry on our backs.
Other parts of life occupy real estate as well, relationships, hobbies... If you imagine a 13-year old boy and 80% of the real estate is give over to sexual desire. A seriously ill person will have most of their real estate occupied by their illness.
With meditation, which I am getting more serious about, you realize you have more real estate than you thought: the mind frees up space by sorting out things that aren't quite as significant and assigning them their proper amount of weight and attention. It doesn't resolve problems, in itself, but shrinks them to their proper size. It is wonderfully freeing.
We don't want to have a lot of extra real estate unassigned to things. It might make us feel lazy or uncommitted. That is why we might want to take extra things on, even when we don't need to. It is fine to have the attention occupied by something meaningful, and freeing the mind from unnecessary shit helps us to refocus on things we actually might care about.