I’m very inclined to go for the free resources a lot of the times too, but honestly when you start reading in japanese your pace will be so slow… 
, that whatever money you spend on manga or books will give you lots … and lots of hour of entertainment and learning. 
You could try EbookJapan for example (and follow this guide to go through the process of buying).
That been said, pairing up whatever resources you decide (paid or free) with something like Kaku (OCR app for Android) sure will make things a bit easier. Here, Tofugu made a review of it too. 