Oh Boy ! You are in trouble. It seems you have totally fallen for that sexy thing that just screams "look at me I am so HOT ".
At the risk of being a crust curmudgeon killjoy a few points to think about.
1) 200 kts at 25 GPH.....Ain't going to happen. Your block fuel flow ( ie wheels up to wheels down) will average 38 - 40 GPH
2) Engines over TBO owe you nothing so you have to be prepared to pay for an overhaul after every flight. For a TIO 540 you are looking at $ 65 to 70 K per side
3) Deice is a mandatory for this class of aircraft. If the boots are in poor shape you are looking at 15 to 20 K to replace them
4) Radar is a mandatory item. Looks like you have the original unit. If it works it won't for long and will cost lots to repair. A new one is $ 20 K
5) A good autopilot is a mandatory item. Looks like you have the original Century 4 system. The Aerostar I used to fly had one. Worked great for years until it did not. After spending $ 11 K over 18 months trying to get it to work the company gave up and put an STEC in it for $21 K
6) You as a relatively low time pilot would crazy not to do a full initial type training course at SIMCOM. 7 K and then 3 K per year for annual recurrent training
7) Insurance will likely be extremely expensive for the first few years. I would not be surprised if the premium is 4 times higher than you AC 520.
Bottom line is it is totally a buyers market for piston twins. Prices are still dropping and supply greatly exceeds demand. What you want is an Aerostar that was owned by a guy like you. That is a guy who has flown their airplane alot and fixed everything as they went along. I bet you have dropped 70 + K on your AC 520 but it will still sell for probably close to what you paid for it. The buyer however will get a pretty good deal. That is the kind of Aerostar you want, one that has had everything fixed.
With respect to N79SR I can bet what its flying history is. Probably pretty regular use until maybe 5 to 8 years ago and then less and less per year with less and less maintenance until the owner finally decides to sell. Airplanes that get regular use generally don't have water in the static system....
Pay now or pay later but you will pay. I think it is always cheaper to shop at the upper end of the market rather than go for a fixer upper.
Sorry for the buzz kill
