Any Tips on Buying?

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When buying and selling used gear with individuals online you are trading away the boring certainty of a retail purchase for the chance of getting something exotic, interesting, perhaps no longer available and possibly a real bargain. The certainty is gone, the risk is high but the reward is potentially great. There's also the thrill of the hunt. You can't have it both ways.

To answer your question, no, I would never make an offer and then back out of the deal. Despite a small percentage of people here who don't seem to have the same ethical standards as the rest, this is a community based on trust and honorable intentions.

Far more often than not I've been well rewarded by going with my instincts about what's a good deal and what's not when the feedback of the seller is good. I can't count the number of deals I've missed because I hesitated too long, but I can tell you about quite a few remarkable purchases I made because I just went for it.
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I don't like backing out of a deal either, but not all sellers are honest, and I'm not one to get stuck just because of ethics. Ethics can't get you a refund.

Even if you "Made An Offer" the "Buy It Now" takes precedent over that offer. You still would have lost the sale.

No, do not make an offer until all of your questions have been answered and you feel comfortable entering into a deal. Once you do make an offer, see it through. If there is a subsequent problem with the item (it is damaged in shipping, or misrepresented in some way), that is another matter. But backing out of a deal because you want to "secure a place in line" before you have done your homework is absolutely not the right thing to do.

By the way, and for what it's worth, I value a seller's feedback far more than I value photographs. Most folks here--especially experienced members--are meticulously honest. If there is a flaw in an expensive piece of gear, of course I would want to see it. But I do not need to see photographs in most cases on anything but the most expensive gear, such as amps or speakers, and perhaps not then, depending on the seller and the description.

I almost never buy from anyone without a solid record of positive feedback.

You should never make an offer unless you're willing to go through with the purchase. If you're not sure, you should make inquiries. If you lose the sale by doing that, then so be it and move on.