:Class A Properties:Cashflow vs Appreciation: Typically, 3-5 years for positive cashflow, but you get highest relative rent & value appreciation.Vacancy Est: Historically 10%, 5% the more recent norm.Tenant Pool: Majority will have FICO scores of 680+, zero evictions in last 7 years.Class B Properties:Cashflow vs Appreciation: Typically, decent amount of relative rent & value appreciation.Vacancy Est: Historically 10%, 5% should be applied only if proper research done to support.Tenant Pool: Majority will have FICO scores of 620-680, some blemishes, but should have no evictions in last 5 yearsClass C Properties:Cashflow vs Appreciation: Typically, high cashflow and at the lower end of relative rent & value appreciation.

Complicating this issue is the need to do a 10-31 due to stepped up value/capital gains tax on half of the land.  

Probably not an issue for seller financing, but make sure there are no prepayment penalties.You can calculate payment and balloon amount easily enough with excel or google sheets.

Can anyone point me to a good guide or advise on any major differences in this type of investing? 

I would hate for this to be an issue.2.

Also discuss with the contractor the time expected for the project if its small, mid or large and if it needs permits and how long would it take for permitting and all, also payment terms, make sure you go with payment terms that are fair to you and the contractor (so many terms but most common is monthly based on completed work with an upfront for materials) and ALWAYS keep the last payment until project is closed (retainage) and you do your walkthrough and if there's any issues you write them down and provide the contractor with (punch list to release the retainer once they're corrected or fixed). read about how to deal with contractors and always ask for references but it really depends on how big the job is, personally I wouldn't spend too much time doing due diligence on small jobs such as door latches or shelving rather on additions, layout change and other scopes.Good luck!

If major renovation is needed, you may need to do a short-term Fix and Flip loan to renovate, then refinance to a DSCR once it is ready to go.  80% LTV is pretty typical for a DSCR, especially with your healthy credit score. 

Renovations may have a major influence on the property's value in some locations while having less of an effect in others.Comparable Sales: To estimate the possible value gain from improvements, look for recent comparable sales (comps) in the neighborhood.

Insurance is a big issue and crisis now in Florida.

Some ground up construction projects and major renovations can save you as much as $5 to $15 per square foot when you consider the benefits of ECO construction methods.