Ask HN: How can I grow single person developed product and scale it.

Hi All, Do not get confused with the title. Just a short background: One of my close friend developed a wordpress plugin which was getting good sales (around 2-3k/month) but he is developing it for last two years.

Though he was happy with the sale (as a passive income) but he was not giving any kind of support for the plugin and most of the email he was not even answering.

Actually he got bored with working in the same staff for last two years, so now he wants me to take over it and keep it growing.

I did some analysis based on old sales invoices so on, it seems there is no such a single solution the software is providing as why the sale was quiet good always.

I am planning to grow the sales. Any idea how can I can grow the sales (e.g it is a wordpress plugin), I planned to improve the support forum, introducing own blog and so on for the product. Can you guys share your experience and give idea how can I grow the sale and improve over all product?

Thanks in advance.