However, it is more difficult to start out with, and is almost impossible (if not impossible?)

you may have better luck with a construction lender, depending on where you are with the project. it's not a good look to be halfway done and then ask for money, but it's not impossible.

I've been told that it is very difficult--virtually impossible--to get someone to buy or lease something without seeing it in a completed state.On the other hand, though, I can't help but be a little concerned. 

Some people cry when they mark it up $10 so it's impossible to keep everyone happy.

Different business folks in a town would feel different about Amz moving into town in a specific community: 1>the real estate investor folks definitely would be excited 2>the renter not so excited 3> Hipster restaurant-er with money to spend would be excited to sell over priced food "experience" 4>Local Subway store would not be excited due to being priced out/sneered at 5>Hipster pour over coffee  and fancy latte "experience" owner would be excited 6>Local $15 mens Barber would not be excited 7> $50 Mens "Hairstylist" place will be excited 8> Some people who have been in that area for years and dont like things to change much will not be excited 9>Politician trying to do favors for Az will be excited ......As you can see there will be many people on both sides ,  it is impossible to make a sweeping statement for a whole community that everyone would be happy with things to come, in fact for many people its a fight for their life and their means on income.

It is hard, not impossible to start part time as an agent. 

Correct, it's more difficult to get an FHA loan done with an illegal unit, but not impossible. 

We have tried on a few occasions only to be told that there are no other properties like it in the area making it impossible to determine the value.

I have the feeling the avalanche is hard, if not impossible, to beat but I would rather know.

It's almost impossible to find a deal on the MLS.