Well, we (I being the American, he the Brit), either one of us or both of us jointly, had to prove to the INS staff at the American Embassy in London that we had either income, wages or a job in the US, not the UK, to meet the support requirement or that we had the assets to meet the requirement (5 times the stated poverty level income for a household of 2). We passed on assets as neither of us had a job in the US. The fact that our assets were tied up in a house in the UK made no difference to INS; they were happy with the letter from a local estate agent as to the value of the property against it's mortgage.
I recommend checking with the INS to be sure.