Question about sell-3d etiquette

[P3D Grant Campos <gc6094@xxxxxxxxxxxxxxxxxx>]

I have a quick question:

If I put an item up for sale and the first response I get starts with
"I might be interested in ... Need some info. . ."

"Moments later I get a response that starts with "I am interested in
your items.  Am I too late?"

Do I sell it to the first person who shows a solid interest (response #2),
or does the first response, no matter how tentative, guarantee the right 
to take as long as he/she wants (or a limited time) to decide whether they 
want it or not?  Or is it case-by-case judgment call?  

Sincerely,

gccampos@xxxxxxx (Grant Campos)


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