Okay, you are in NY State, which has some programs you need to look at.

http://programs.dsireusa.org/system/program?state=NY

To be honest, in terms of actual savings, the first thing to do is reduce. Start with an energy audit from your power company or one of it's contractors. Replace your light bulbs with LEDs and CFLs. Get a programmable thermostat. If your furnace is old, look at replacing it, looking at the energy efficiency ratings and rebate programs in your area. If you have an electric car, look at the charging station and it's rebates.

Back to solar incentives - the biggie is the 30% federal tax credit. There's a 25% state tax credit (up to $5000). NY has an incentive MW Block structure, which basically that as more installations are made, the lower the state grant given back. There are also various more local programs like property tax incentives and sales tax exemptions, as well as an incentive program for the electricity you product.

The NY-Sun website has a list of pamphlet of things to know (like you need a participating installer for some of these incentives) Make sure you know if your installation estimates are gross or net. Some companies will give you a quote net - after all the credits. You want to know both, because you won't see some of those credits for months, you need to know how much to pay up front.

Also, http://pvwatts.nrel.gov/pvwatts.php will give you a quick estimate of your probable output and prices.

As for pricing, the current ballpark figure near me installed is about $3.50/w - so for 7kW, you are looking at $25K, give or take (I had a similar estimate done for my house a little over a year ago at $27K). Also, you need to know the state of your roof. If that's an asphalt roof, you have to ask yourself how old it is and whether it has to be replaced to make sense to put racks up there.

Let's say you have 3kW in the most efficient area of your roof. (Those 12 panels that are dark red). Rough back of the envelope estimate here - that might run you $11K to install. Call it $1500 back from the state incentive. So, that's $3000-ish in federal tax credits, another $2500 in state tax credit, so you're running $4-5K out of pocket after the credits come back in April. Assuming you were somewhere like New Paltz, that would run you about 3,500kWh in electricity, or call it $500/year - call it a 8-10 year payback.