If it's truly valued at $400k, you could pull out up to $300k with no tax implications whatsoever (you'd be taking on debt, not incurring a capital gain).With regards to depreciation, engage a great CPA who understand and specializes in real estate investing, and ask them if it's possible to use a cost segregation study to take accelerated depreciation.

Is there a single comprehensive book/resource which could be a good bible to learn from/study?

take the money and get rid of the hard money guys. increase your cashflow and maintain your property.  

The object of the game is to reduce/eliminate your cost as low as possible while maintaining positive CF, and let your tenant pay for the rest from the rent. 

You may want to talk to your CPA about establishing your home as your principal place of business so you can deduct future travel expenses) "Local transportation expenses: You may be able to deduct your ordinary and necessary local transportation expenses if you incur them to collect rental income or to manage, conserve, or maintain your rental property.

For example, the claim that undocumented immigrants are associated with increased violent crimes has been debunked by nonpartisan studies, as has the claim that undocumented immigration is associated with increased drug crimes.A landlord who makes rental decisions based on such generalizations could run afoul of federal and state housing laws.

I just recently began studying wholesaling.

How long should I study before I begin my journey to buy and renting my firs mobile home, without becoming a person that looks into it so much and never take action.

Regarding final punchout projects, that may free up some of your time but it also gives you an opportunity to observe the almost finished product to help maintain quality control.

Shoot me a PM and I'm happy to share some BRRRR case studies you might find useful.