Acquired, developed, marketed, and sold dozens of apps to return 3X investment in under 2 years. Funnel optimization: acquisition, engagement, retention, and monetization. Co-founded and sold GoFastCab. 250K users in 18 metros.
I am pretty sure exitround is inactive and don't think it is the best match for app sales.
Flippa, as Lee stated, is a great place to list your app. Also is Fliptopia. https://www.fliptopia.com
The latter is focused on apps and has their own built-in escrow service, which is usually efficient. Flippa users usually use escrow.com, the last time I checked. I have done several buy and sell side transactions, using both Flippa and Fliptopia.
Congrats, that is quite an accomplishment. You could probably get some angel or VC interest, depending on how well your app scales. At some point, you will be able to get loans based on your income stream. It also depends on how much you are looking for (and need). You already have at least $7000 coming to you.
The two main online marketplaces for apps are Flippa and Fliptopia. Apps usually sell for 10-20 times the last month's revenue. Listings selling for over $50K are few and far between; must close at $500-$5000. For assets worth considerably more, you would need to find investors or a company where there would be synergy.
For anyone needing help in this area, feel free to reach out to me.