Hi,
My name is Macy. Your idea is great. Housing is a huge issues and where I live our housing margin, last time I checked, was at about 1%. I would love to help you build awareness for your app. My day job is in insurance so I actually know lots of landlords myself.
I think before entering any arrangements we will want to chat about your goals.
I am not sure how far along you are in the process of marketing your app but you will need all your social media accounts ready to go along with your website. You will also want to make a card or something for yourself with a friendly photo. People want to see who you are before investing their time and money. I think marketing to individual realtors could lead to finding landlords, but I think you should direct your sights at a company like SVN. They are a national commercial real estate company but they also manage commercial residences like apartment complexes. You may not get a ton of landlords but one landlord could lead to multiple available residences. I have contacts there so I could get you connected. I also can also assist you with any of your marketing platforms but seeing as you have developed an app you probably don;t need help setting up a facebook.
I hope we can work together and I look forward to hearing back from you.
Thanks for your time,
Macy