I probably don’t waste my time in starting forum within a same blog, because it’s just make whole things very complex and make blog database heavy bloated. It is same like in your old computer you’ve install so many software, which make computer to load very slow, same thing will happen to your server. You can’t put so many things in single server. If you go with VPS then it’s fine, but again you’ll look for cheap price, so the end will never good unless you know all things yourself.
You should look to other successful blogger, do they use any plugin to make forum site on same blog or use forum software like discourse, mybb, vBulletin on separate server.
I have done so many things like that in 2013, but it’s just waste of time.