1985 Civic value

My bf recently bought an '85 Civic 4 door,  
automatic transmission with 51,000 miles.
However,  it sat in the harsh Texas weather
undriven,  unmaintained for 4 years.  The
tires were bad,  the fan stopped working
asap,  now the battery or alternator is dead.
The people who sold it fo him seemed "nice"
and he says "honest", but I felt they were
overly nice and deflected from the
mechanics of the car by emphasizing tge
sentimental value of it. (Granny owned it and
was from the same state as my bf. ) He paid
750.00 for it. I say he was swindled as rhe
car sat for so long and likely deteriorated
with dust,  mud,  rain,  freezes,  no
maintanance. He disagrees as says the low
mileage makes up for any issues. I think if
you buy a car likw that,  be prepared for
repair after repair.  Was 750 a fair price? Did
the seller hijink my easily distracted bf with
their sentimental stories about the car?
Does 51,000 miles make up for it being
discarded and unmaintained for so long,  
along with being 33 years old?
Thanks.  I got swindled once by a used car
dealer....what a shock...but I was desperate,
new to town,  needed a car and did learn
feom my mistake.