Really depends on what you are looking to do / what markets.

For a 3 unit building with one unit as a commercial space/retail space I would use either a 7 or 10% vacancy factor and perhaps higher depending on the viability/business strength of the restaurant.

Depends on the square footage of the house to begin with.

Michael,With regard to insuring the condo units, the amount of building coverage you should have on your policy depends on what parts of the building you own. 

This way, you can have passive income coming in from multiple properties regardless of where you are living at the time.Ultimately, the best strategy for you will depend on your long-term goals, risk tolerance, and level of involvement you want in managing the properties.

Your Credit Score: 680+ or 700+ will get you better terms depending on the lender. 660 is the minimum for many lenders.

Just depends on goals and needs 

If the fees reward the purchase of more and bigger properties disproportionately, I'm wary and likely out - depending on, or in conjunction with the next point...- What are you investing in the deal? 

Speaking from private/hard money terms, the loan would most likely be considered a delayed purchase if less than ~5 months depending on the lender, and no financing was used on the original purchase.

Much depends on the experience of the person your lending to.