I am having first hand experience with this as I'm applying to both.
The bulk of DO schools, I've found, require at least $1000 by December 15th, or within 30 days of your acceptance. As a stronger DO applicant and weaker MD applicant I foresaw myself getting some acceptances long before i'd hear back from an MD school and being out the money I put down on whichever DO school I got an acceptance to and liked the most, you know.
Luckily, there are SOME DO schools that are a bit more reasonable with their deposits. AZCOM's is paid in $500 deposits I believe so you'd only be out 500, not a thousand...This is also the case with DMU..OUCOM is nice as their first deposit is just 100, then another 500 isn't due until June 15th. There are, I'm sure, more schools like these but these are the ones I'm applying to so I'm familiar with them. Check out the school websites to find out what their specific policy is.
It is a bummer though, with having to put down so much money and potentially be out it completely if you later hear from another school, be it MD or DO that you want to go to more. The MD schools have much lower and later deposits, so don't worry about those.