I am not sure about the current used gun values on those HK's, but the HK45C will be the most expensive used gun among the 3 you listed. The least expensive, IMO, would be the USPc .45. It's just because the HK45C and P30 are more recent model and sought after. I am sure other members will have better ideas than I could ever try.
Seller can send the gun to your local FFL himself, or use his FFL to send to your FFL if your FFL does not accept shipment from a non-FFL or individual. Regardless, you will have to pay your FFL to run a background check and his transfer fees (ranges anywhere from $10 to $50). Shipping is what you will have to negotiate with your seller unless it is included in the price of the gun.
There's no buyer protection when you buy from a stranger. This is no eBay. I am not 100% positive on this, but even if you pay with PayPal (sent as gift), there's no recourse should the seller disappear. So you just have to trust your instinct or do due diligence to research about your seller. I have only bought once from a seller on this forum, but the transaction was flawless.
Good luck, and welcome!
Seller can send the gun to your local FFL himself, or use his FFL to send to your FFL if your FFL does not accept shipment from a non-FFL or individual. Regardless, you will have to pay your FFL to run a background check and his transfer fees (ranges anywhere from $10 to $50). Shipping is what you will have to negotiate with your seller unless it is included in the price of the gun.
There's no buyer protection when you buy from a stranger. This is no eBay. I am not 100% positive on this, but even if you pay with PayPal (sent as gift), there's no recourse should the seller disappear. So you just have to trust your instinct or do due diligence to research about your seller. I have only bought once from a seller on this forum, but the transaction was flawless.
Good luck, and welcome!