There does not seem to be any part of these forums specially devoted to hiring a programmer, you just publish it and it appears on the top of all threads. That should be sufficient for the possibly interested programmer to contact you.
If you want to spend money for an app, I’d suggest first becoming a member here. That would give you more weight, so to speak, showing your commitment, and would also enable you to have an apps server. Without it, you are making the task of a would be programmer more difficult.
Try the Existing Plugins First
I second the idea of looking at the existing plugins and buying one or more of them before doing anything else. Once you have tried them, you will be in a better position to explain to the programmer what you want and what you do not want in your version of the plugin. And it may also happen that the existing plugins are quite sufficient in the first place, you won’t know until you tried them.
The programmer will also have that plugin and its source code, so you would be on the same page with the programmer. That is very important, as there can be no successful plugin making without a project and a goal first. You should write as detailed a project as you can, and you must state the goal, so the programmer knows when the job is finished.
Be Precise in Your Project
Sometimes a single word means a lot. Once I was hired to create a plugin that downloads an MP3 file and plays it. When I finished it, the client said: “Oh, I want it to play non stop, even when you leave the app.” So I scratched everything I wrote up to that point and had another round of coding, for the same amount of money, so to speak. (For the technically minded, the first version was written as a fragment, the second version was written as a service in Android.)
In case of an RSS plugin, the difficulties might arise if you wanted to commission a general RSS plugin, one that could read each and every RSS feed out there. For best results, you should specify the exact feeds that you want your plugin to be able to read and enter them as a part of the plugin initial specification.
How Much To Pay For the Plugin?
As for the money involved, that will differ wildly. I see people here being paid 100 dollars per plugin, then some are paid $300, some are requiring $500 and getting the deal, and if you want someone to write you an entire app with 5-10 separate and original plugins, that may well end up in lower four figures. You will never know until you start negotiating.
Unless it is someone that I have already been working before, I insist on down payment — the entire amount in advance. Again, there are no rules. In any case, be prepared to spend a lot of time working with the programmer. Usually, it is through email and Skype, but there are other channels as well. You must have your own vision of the finished plugin and may want to impress that on the programmer, however, you must also respect what the programmer has to say. Some things are not (easily) possible on Android although they may be readily available on iOS, and vice versa.
Allocate at least several weeks for the plugin to be ready for production. 3-5 days for the initial effort, 3-5 days for the coding and testing, 3-5 days for writing documentation, something like that. If there are nasty surprises along the way, it may take much longer.
What Else Can You Do To Increase the Chances of Success When Commissioning a Plugin?
You should already be proficient with various aspects of the app development cycle. I suggest you have at least one Android app published before commissioning anything, so that you and the developer are on the same page right from the start. After all, you are commissioning one plugin only and that will have to fit with the rest of the app. Programmers are often not that great at design, or do not want to get involved with it, so you will have to supply your own design for the app — the color scheme, icons, menus and options etc. The programmer has to be given an icon, they will not develop it for you just because they can.
Commissioning a Plugin Is a Part of a Business, No More, No Less
In the end, commissioning a plugin is a business decision. It must fit into your business plan for the app, and if it cannot, don’t commission anything until you can prove to yourself that the existence of the new plugin will turn tables into your favor in the app stores.