I want to buy a PAL VHS from eBay. My TV will accept a PAL signal but
I think my VCR is NTSC compatible only. What would happen if I use my
PAL VHS in my NTSC VCR? Will I get any recognizable data on the
screen? Will doing so damage my equipment or my VHS?

Here in the UK, most (newish) VCRs play PAL & NTSC.

However, they only record in PAL.

If your VCR will only play NTSC then you should not buy a PAL VHS
because it won't play in your VCR.

You may not damage the VCR but why bother?

For what it is worth I have done the opposite and played an NTSC tape
in a PAL video, the sound was perfect but the video was in black and
white... I suspect this is what will happen in your case too.  The
difference between NTSC/PAL as I understand it is mainly down to the
number of lines that make up the picture (PAL being superior).

I found this information on the web:
url:  http://www.geocities.com/~sbwebmaster/articles/concertreviews/palntsc.htm 

"PAL VHS videotapes CANNOT be played on standard VCRs in territories
that utilize NTSC VHS format, which include the United States of
America, Canada, Mexico, the Carribean Islands, Central America and
Japan. Accordingly, if you live in a territory that utilizes the NTSC
video format, you will have to take the PAL videotape to your local
video/photo-finishing shop and get a NTSC dub in order to view the
tape. A PAL video in a NTSC VCR will give you lots of snow and a high
pitched squeak"

You probably don't want to buy more stuff, but there are universal
format VCRs that will let you play almost everything. If your TV
accepts a PAL signal, you might consider one of these VCRs.

At work, where I deal with dubs from around the world, I use a Samsung
SV-5000. This VCR handles 5 seperate PAL formats, 3 SECAM/MESECAM
formats and NTSC. It will  read almost any format and output to one of
your choosing. It costs about $300 unfortunately.

You might use that or a similar product to make dubs to your current
NTSC VCR. When making dubs, see if you can strip out the Macrovision.
Some VCRs do it automatically. This is a screwed up copy protection
scheme that messes up the picture, even if you have a legitimate
reason to copy a tape.