My theory is that, in real estate photography, your lens is the most important piece of equipment. And many times, your high quality ultra-wide lens, is the most expensive equipment you purchase. One of the best ways to decide which ultra-wide-angle lens you want to purchase is to rent it before you decide to purchase. You can rent many of the lenses I have listed in my lens table for a few weeks to make sure it's the lens you want. Prices are reasonable.
There are several equipment rental sites that allow you to rent glass if you are in the same country. Here are a few:
I'm not recommending any particular camera rental site because I've never used any of these sites. However, it appears to me that lensrentals.com has the biggest selection of ultra-wide lenses. For shipping and customs reasons, these sites typically rent in one country. For example, rentglass.com only rents in the US (lower 48 states).
If any readers have used equipment rental sites they can recommend please leave a comment.