I think the question is how much collaboration do they really do on these projects? The show makes it look like it's a joint decision which house to actually buy and how much they pay. Then Christina does the design and has to convince Tarek it's worth it to spend the $$ (he always gives in), and he seems to do most of the supervision of the work. Then they both work on the sale end. If that work can be split up more (and maybe it is in real life), they might be able to pull it off. Otherwise you're talking about not only splitting up the show but their business as well. That could be quite damaging financially....