percentage of cash to use for downpayment - standards?

[Amanda Smith]

I am buying my first investment property but can't find a lender that will go less than 25% down for 30 yr fixed, unless it is an ARM. Fixed will give me some peace of mind. However, Paying this much down will end up using 40% of my liquid cash. Is there a ratio of savings that is best to use that people go by? I am feeling like it is 'irresponsible' to slam down this much cash for some reason. The property will have an ROI between 11.8% and 14.2% depending on rent I get. If I have this supplemental income I won't have to work anymore, barring no unforeseen rent decreases due to economic crashes.