Technically, WordPress is built in PHP. If you are choosing between having a site custom designed in PHP versus WordPress, WordPress will be much less expensive.
The main thing to understand with regards to WordPress is that it requires a lot of maintenance to keep it secure and running right.
It's open source, so when updates come out, you get the updates at the same time as the hackers. This in conjunction with the fact that it's a very popular platform, makes it a target for hackers.
Personally, I'd recommend you add a 3rd candidate into your mix of options. That would be some kind of a hosted solution. Just do a google search for, "Hosted Real Estate Agent Site" or "Hosted Property Management Site."
These will usually be much less expensive as far as initial cost goes, however, the monthly upkeep can seem a bit high. That said, maintaining WordPress can cost $50-100/mo, when done properly.
Hope that helps.
Thanks,
Justin
Website Developer with two decades of experience