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Someone should please help or put me through on how to make residual income on this platform.

Here is a small guide : https://poloniex.com/support/aboutMarginTrading/
Look also at youtube, there are many videos about it
I do not use much poloniex, I use only for exchange

Why is the STEEM wallet on Poloniex consistently down for maintenance? Is this a Poloniex or STEEM issue?

I have no idea but if you are going to buy or sell steem use https://blocktrades.us/.
Poloniex has continually STEEM under maintenance.
if you have steam on poloniex account ,Exchanges it with to another CryptoCurrency And transfer them to other wallet safe.

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