Who has $235,183 lying around in a bank account? The average homebuyer in Silicon Valley, apparently. That’s the median down payment for a home in the San Jose metro area — and it’s on the rise. In the third quarter of 2023, the median down payment in San Jose reached nearly 25% of purchase price, up from 23% in the first quarter, according to data from Realtor.com. In San Francisco, the median down payment increased to 24.4% from 21.8%. Even with sky-high Bay Area purchase prices, those percentages are higher than anywhere else in the country — and significantly higher than the national avera…