You can select any of the above fields based on your skill sets to create second income source. There is no dearth of opportunities, only thing matter is to identify the right one, which suits you. There is no shortcut to success but you have to start journey from some point. Recession can push your career 5 years back but with proper planning you can minimize its impact and remember Bad Times also don’t last forever.
Investing in Index Funds – I use Vanguard for this, but there are several reputable sites out there that allow you to do the same thing.  It’s a good way to invest excess cash that you don’t need now and use it to diversify your portfolio.  I’m not going to make a specific recommendation here, but Vanguard does have a page that will make a recommendation to you based on your risk tolerance.  This is generally going to require more up-front money than Lending Club (probably $1,000+), but if you have the money, it’s something to consider.
Portfolio income can come from multiple sources – interest/bond coupons, stock dividends, financial strategies including derivatives and capital growth.  Each offers some cash flow and some also offer potential capital gain with some risk from liquidity and volatile prices.  In this low-yield environment, many investors rely too heavily on cash flows and to pursue this are venturing further into riskier areas than they’d normally consider.