1)some exterior deterioration in the wood trim in various places
Impossible to say how big of an issue this is. It depends on how much trim there is and how much needs to be replaced. Could be $500 or $5K
2)The plastic flashing on one or more of the plumbing vents are split, cracked, deteriorated, or lifted. Repairs are necessary
This is either a DIY or $100, to fix a couple. But, at this age, it's normal and probably a good idea to replace all of them.
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3)The is rust in the metal vent vovers and flahsing on the roof.
Again lacks clarity. If it's just cosmetic and paint will solve it, it's less than if it's rusted out and needs to be replaced. But either way, not expensive.
4)The flashing at the chimney may be an eara of potential leaking
Is that all he said? He should have gone into more explanation and also said if there was any indication from either the attic or inside the house of actual leaking. It's easy for anyone to say flashing at a chimney MAY be an area of POTENTIAL leaking on most houses.
5)Additional vent openings in the attic were recomended to be installed.
Good idea and should cost a few hundred bucks.
6)Unable to fully inspect the attic due to personel content
Not clear how much he could see and how much he could not. Again, if he took the time to add "I could only fully inspect the front 2/3 of the attic.... etc, you'd have a better idea of what he actually saw. Did you go with him? What did he say about the area that he could see?
7)It was noted that there was some stains or damage on various areas of
the ceilings and walls.
No clarity here either. Did he probe with a moisture meter? That should have been indicated. Were they in areas that could be attributed to the chimney flashing or plumbing vents, roof holes? Or where they from soda pop?
8)Life before replacement of roof - 3 years with maintenance and repairs as needed.
Probably the original roof, so no surprise here. This is the highest cost item on the list and the one you should focus on first.
As others have pointed out, this is all typical for a 26 year old house. I'd get quotes from contractors to fix all of this and then negotiate for a discount in the price of the house. The quotes will add up to X dollars. I would expect to get most of it taken off the price, but exactly how much depends on how well priced the property is to begin with, how much you want the place, etc.
Also, you said it was a townhouse. That term is used very loosely. Is it a detached home or is it a condominium that is attached to and shares a common roof with other units? If so, the roof and related issues, vents, flashing are probably not your responsibility, as they are maintained/replaced by the association. I would get a complete copy of the association documents, master deed, bylaws, rules/regs and read them thouroughly.