Everyone's ROI will depend on the amount of money you invest in the contract. You can upgrade over time once you have a contract to upgrade. This: https://www.cryptocompare.com/mining/genesis-mining/dash-starter-gemini-2-year-small/ << Appears to be the smallest one you can start with;

HOWEVER, if you plug in how much you plan to purchase here:

https://www.cryptocompare.com/mining/calculator/dash?HashingPower=0&HashingUnit=MH%2Fs&PowerConsumption=140&CostPerkWh=0.12

<< You can see what is estimated for your returns on any amount of MH/s you are considering.