Someone is selling me a Red-Tail Boa... but it has a lump...

[NightLad]

I really liked her.

What would be a fair way to go about it if I did decide to buy her? Ask him to take her to the vet first? Ask him for money back guarantee if she gets sick from it?

A trip to the vet + expenses for tests (depending on what they are) might cost as much as he is trying to sell her for. So, I doubt he will be willing to give her a medical prior to sale.

Asking for a money-back guarantee might be feasible, but it will depend on the guy. If you politely express your concern about the lump, and tell him that you plan to pay for a trip to the vet after the purchase, he might be understanding and go for it. After all, if he is really sure it is nothing and she has had it since he can remember, than why not give the guarantee? On that note, at the time of sale (prior to cash changing hands), ask for a receipt with the guarantee listed on it.

If he balks at the suggestion, than as much as you might like her, I'd take it as an indication that everything may not be as simple as it seems.

When I bought my BP he was raised on live rats, but I indicated to the seller that I wanted to switch to F/T. He happily gave me a money-back guarantee if he did not switch, and even gave the option of returning him so the he could switch him over if I wanted. (It was a tough battle, but I eventually got him to switch. hehe)

She does look absolutely stunning, but go with your gut.