Right now it takes around 48 hours to begin receiving masternode payments. Once you start getting them you can calculate the number of expected payments per day with the following formula.

number of blocks per day/number of masternodes=number of daily payments per masternode

So, right now you can expect 1440/974~1.47 payments per day. With the current number of masternodes on the network masternode payments are 29.25 DNET, so you are looking at about 43 DNET per day per masternode, on average.

These numbers reflect as things stand right now, and could change daily, or even hourly, if the number of masternodes changes.