why some real estate investor fail ? and how we can avoid this failure?

Plus, you have risk of being a principal in the transaction as a wholesaler.One could (and some may say should), consider converting your presentation to motivated sellers to a listing presentation and not offer to buy it yourself at all.For example, with your managing broker's permission, you could get either a full listing contract and market the property properly, get your seller maximum dollar (whether that's to an investor buyer or owner occupant buyer).

Lending is about risk versus reward.

However I need a strong agent who can propose fundamentally sound investment SFRs with solid math based on our cash position and risk appetite. 

It is state by state and you will have to research your state laws, however with the potential for legal ramifications and the goal to wholesale, it may be best to get your license to avoid any risk.

We only have one life so take risk, cause none of us are gonna make it out alive.

They then turned around and sold the empty plots of land to investors that did not want to go through the headache, nor did they want the risk, of waiting a year to receive approvals for their investment.

@Caleb Anderson Knowledge decreases risk.

Also a concern here is the addition being an approved/permitted spaceSection 8 not withstanding if the addition wasn't a permitted addition you'll likely will be taking a significant risk that should a tragic event take place there with a loss of life or serious injury you'll have no place to hide as most insurance companies will not pay your claims plus the civil and criminal penalties are severe!

You gotta take the risk to make things happen otherwise you will never find the deal.I usually get the deals by scrubbing MLS and wholesale deals come to my email all the time.