Disclaimer: I am not a lawyer and I don't claim to have extensive experience with lawyers. But based on my personal experience and some logic ...
I don't know what typical fees are for a lawyer in Maryland. May well be higher than here in Michigan. But I see @phillip found a source that says typical lawyer fees are $100 to $300 per hour, which sounds plausible to me. I hired a lawyer last year who charged me $150 an hour, which I think was on the low end but not like a leap up and cheer bargain.
Last time I hired a lawyer before that was to get a new will written. A pretty straightforward will. She charged me a flat $200 and I'd guess did maybe 2 hours work.
Before that I consulted a lawyer about a minor child custody issue. The gist of it was that he explained the law to me and discussed my options. He spent about half an hour and charged me $50.
Next question is how many hours you expect the lawyer to spend on this. As you describe it, you want a lawyer to review the document and explain it to you in layman's terms. You're not asking the lawyer to draft any new documents, or to represent you in court. You just want him to read some papers and explain it to you. How long should that take? An hour or two? If you hire a lawyer who is experienced in real estate law, he should be familiar with these sort of clauses and would not need to study it carefully and do extensive research. He should be able to just read it over and say, yup, I've seen these before, here's what in means.
If I was hiring a lawyer for that here, I'd expect to spend -- just guessing here, but I'd think the ballpark would be $300 to $500. In Maryland it's probably more because that's a higher cost of living state. But $1500 for an initial retainer and add to that seems pretty high.
As I say, if someone else has specific experience with law firms in Maryland and this particular kind of case, please chime in.