The Battle King Is a Miser

It's pretty good, worth reading. The combat system in this novel involves summoning battle spirits from the main body, similar to the guardian spirits in Soul Street. The male protagonist is a poor kid who values money a lot, which makes him seem to have ambiguous relationships with several women to outsiders. The reason... Well, it's about making money! The writing isn't great, but the plot is good so far. I'll give my feedback after I finish reading it or if there are any flaws.

Is it a single female lead? Is the protagonist invincible?