SolarCity, Elon Musk’s fast-growing solar leasing business, broke ground Tuesday on a huge factory in Buffalo, N.Y., to build high-efficiency solar panels. In each case, Musk’s companies are trying to ensure a future supply of low-cost, high-quality equipment to fuel their expansion. [...] each project has attracted significant taxpayer dollars. [...] as part of an agreement with the state, the company will spend approximately $5 billion on capital costs, operational expenses and other costs associated with the facility during the initial 10-year lease period,the filing said. By comparison, Nevada officials offered Tesla tax breaks worth more than $1.2 billion to entice the automaker, based in Palo Alto, to build its battery factory in their state.