What is the best route to ensure that our money is backed/secured - promissory note and mortgate?

Any thoughts would be appreciated.Thank you,SteveIf there are multiple secured liens on the house, it depends on who is foreclosing. 

My question is should I make my offer and worry about getting financing later or secure pre-approval first?

With market rents, coming up with first/last/security deposit can approach $10k in some neighborhoods, which can be a difficult check to write even for professionals.

I get emailed deals regularly but have not taken the steps to make a 100 plus unit happen yet. 

As well as checking out the previous and ongoing BP blogs and webinars, it will be a good habit to check the "Recent Forum Posts" every day, follow the topics that are of particular interest, and post comments/questions regularly too.

I have always been interested in real estate investing, but the security of full time employment & raising my family took priority.

The Mortgage (or deed of trust in some states) is the legal instrument which secures the property as collateral for the loan.It is important to think of it in those terms as they have two different purposes.

And what are the best things to look for to buy a house under market value to secure equity?

I no longer live in the islands, but I maintain my company there remotely and regularly flip properties.