For instance, depending on your location insurance costs could be much much higher than indicated in the book, construction costs are a lot higher, etc. 

Usually, tenants are receptive to the idea but I also wonder if tenants with a higher credit score care less about this feature than ones with a lower credit score who are actively working to rebuild their credit?

More people see your property, the higher likely hood of securing a tenant in a quick amount of time (all things equal).

I’ve had several investor clients go with a new (to me)/ unproven lender because of a slightly lower rate promise only to get burned by that lender (closing costs were higher, appraisal costs much higher and appraisal was a nightmare, main point of contact gave us the clear to close as we passed our financing contingency then just before closing someone from the underwriting department we previously didn’t know existed said we need a few more days and seller didn’t agree because they had a higher backup offer, jeopardizing the earnest money and losing the property, etc).

Quote from @Chris Seveney: @Francisco AvancenaThere are specific lenders who will do land dealsBut of course not as many as traditional real estate.The key will be skin in the game - typically for land because it is less liquid than a home the lender will want to have a lower ltv on the deal I fund land flippers currently in  CO FLA WA ID MT NV AZ OR TX SC GA VA  one thing about land though LTV is lower and RATES are NOT the same as typical HML rates are higher for raw land but its a specialty niche and a business that I grew up in..

You’ll probably pay a higher sales price and a higher interest rate as well. 

The tradeoff for doing it all alone is higher risk and a much slower pace.

The Norada Capital promissory notes do offer a high rate of return (interest), but I would not classify them as "high risk" because of the higher interest rates.To correct your comment, they ARE backed by hard assets and collateral.

A safe baseline is 5%–10% for vacancy, with C class properties often leaning toward the higher end due to more transient tenant populations.As for maintenance, the percentages they’re quoting—2% for B class and 7.5% for C class—are on the optimistic side, especially for long-term projections.

Stay away from the condos as they are going to continue to have higher HOA's and insurances going forward in Florida.