@Martti Eckert in our opinion, you'll need to be really familiar with construction, including costs, or be able to find somoen on the ground you can REALLY trust (but still verify).

To confirm my recommendation ask him for references at his current developments, I bet he won’t give you names and will make up an excuse!

Even at $60,000 a unit - that is a $1.2 million deal... and realistically I bet they will be over $100,000 each... all just a guess... but when you get into these price points and you are "new to real estate" as your title in your post suggests - I think you are probably getting in over your head for a first deal.  

Typically when you see "cash only" the agent doesn't believe the property can pass a home inspection which isn't relevant for construction loans in most instances and there are plenty of banks, hard money lenders etc. who offer construction financing on distressed buildings.

The type of information needed depends on if the building is being constructed in the future or if the building already exists.

In my opinion, that is a riskier bet because you have to have a big pile of cash for contingencies.  

There has been a ton of new construction for housing the past 4 years and that’s why vacancy rates are 10-12% and rental rates have dropped the past couple of years. 

The biggest things you can offer in development are finding a deal, finding capital, or construction expertise. 

Also, construction is in all time low, so that factors into the need for rental properties. 

The owner needs to know you are solid, a good bet.