Yes they live on the same farm. The only other option was to sell the farm. But neither wanted to. Neither had the money to most the other person for their half. They have different houses quite far apart, more like neighbors.
He likely assumes since she got the massive house and he had stuck in the double wide, the cottage should come out of joint funds. It isn't like he is asking her to pay private money., simply yo use their joint business's account, the money from their businesses, to build.
It probably will come out of their business expenses. When they were married they built the house custo.m for both their special needs. Matt should have the same choice to do so now that they are divorced. Only build it on the other side of the farm. The homes now are to close. Also, I can understand the need to take down all the security cameras Matt put up. They should only have a few by the gates entrance. If someone wants to come in unapproved, camera's won't stop them. Plus the dating for either of them can create a problem of jealousy.