This is a reasonable list of repairs…for a 20-year old car costing $3k or less. For a $20k car, GTFOH. At that price point, the seller needs to fix everything that is wrong–including cosmetic issues, or you should keep looking.
To be honest, I do not believe that 2017 CX5 with 100,000 miles is worth anywhere close to $20k, even in perfect condition, especially from a private party. This vehicle cost about $25-30k when new, and now after 5 years and 100,000 miles, I would not pay more than $15k for this (assuming decent overall condition).
You want to pay 20000.00 and then another 2500.00 ? That is insane . 20000.00 should get you a vehicle that does not need work to start with . If this is a private sale tell them to fix the stuff then call you and then pay only 20000.00 . Which I would not pay in the first place.
Numbers 2, 4, 5, 6 and 7 are maintenance and upsells, not urgent. The fluids should be replaced @ 100,000 miles. You could drive the vehicle for 6 months as is or you could negotiate this maintenance as part of the sale.
The oil leak is for the perfectionist, likely not dripping or the dealer would have repaired this.
Front brake replacement is questionable. Minimum brake pad thickness is 1 mm, many of my co-workers recommend replacement of pads 4 and 5 mm just fishing for work.
Some of my co-workers typically find $5000 in repairs during a used car inspection on a vehicle like that. One must discriminate of what is reasonable and necessary. An oil stain on the oil pan and an A/C evacuate and recharge are not urgent and likely unnecessary.
To me there is not enough info provided to even hazard a guess.
Brake service based on what? Pads down to the minimum, rotors gouged, or what?
AC service also based on why?
Rusty oil pan and slight oil leak means what? Leaking where there is rust or the pan has rust on it and the leak is coming from a missing or re-used drain plug gasket?
If an oil pan of all things is rusted bad enough to leak then I have to wonder what else is rusted bad enough to be a problem; if not now but soon after.
A rusted oil pan is not commonplace, and to–supposedly–find it on a 5 year old vehicle is extremely rare. I have to doubt either the honesty/integrity of the mechanic who inspected it, or I have to wonder about the overall condition of this vehicle.