I slow-rolled a very similar decision last year and here's what I ended up asking for, in the order that mattered.
First, a content calendar for month one before you sign, with actual post topics, not categories. "Market update" is a category. "Why a lender asks for two years of bank statements" is a topic. If they can't produce eight real topics in your subject area, they don't know your subject area and you'll end up writing it yourself.
Second, who writes and who approves. Ask whether the person you're talking to writes the drafts or hands them to someone else, and ask to see two samples from a client in a similar field. Then get the approval loop in writing: how many days before posting you see drafts, and how many revision rounds you get.
Third, and this one is specific to you, lending and mortgage advertising has its own rules about what you can say about rates and terms, and those vary by state and by what license you end up holding. A general social media freelancer will not know them. Whoever reviews your content for compliance needs to be a licensed professional, not the content vendor.
On the three month minimum, I'd ask for month one standalone at the same rate, or one month at a higher rate. Plenty of people will take that. Someone who won't discuss it at all is telling you the minimum is where their margin lives.
Price ranges vary enormously, so I wouldn't judge $1,200 in the abstract. Judge it against the calendar they hand you.
