Henry as you probably know, what works for SEO purposes can change daily with algorithms used by search engines.
You want to strike a balance: Repeat important keywords, but don't use hidden keywords, repetitive keywords or other tricks (no kidding, I saw a site from an agent in my office whose webmaster had hidden "service" at least 3 dozen times - enough to keep her OFF some major search engines!).
Use your specific keyword in your page title; your headline; use it in the body of your copy at least 2-3 times, maybe 4-5 but not more. Include it in your meta tags, but don't get carried away - keep keyword meta tags under 300 characters if you can. Use it again in your description meta tag, but again, keep that one short, like 60-100 characters.
Use it but don't OVER use it. And do it for EVERY page on your site (the mortgage page, the listing page) - using the specific keyword for that page in the meta tags.
I have a guide from a site service I use, and it's free, email me offline at guide@seucaskey.com and I'll send it. It's a PDF attachment so be sure you can accept it. If anyone else would like a copy, please use the same email and don't post your request here as a reply, thanks!
Sue