The three checks, in order
One: ask what the offer assumes about the roof, furnace and wiring, and get the reasoning, not just the figure. Two: ask what could change the number between now and closing, and get it in writing. Three: ask whether they buy and close themselves or pass the lead to another company.
Why the "as-is" number is usually lower, and that's not automatically bad
As-is pricing reflects the buyer taking on repair risk and skipping an inspection-contingency renegotiation — a lower number for more certainty is a legitimate trade, not a red flag by itself. The red flag is a number that drops after signing for no clearly explained reason.
Getting more than one offer is normal, and worth doing
There's no obligation to accept the first offer, and comparing two or three tells you more about whether a number is fair than any single conversation can.