I faced thus some time ago and was faced with a challenge because some many of my deals gave long gestation times or are complicated.So, I offer a total % of profit and have broken down as half a fee for info about the opportunity, and the other half for contact info, usually in the form of an intro to all principals. 

I actually am a teacher myself and my former favorite principal is one the superintendents in Marysville SD.

My principal residence in Hawaii tripled in price when I sold, and I came back to the Bay Area in 1990 and worked for a couple of non profits while investing in multi family in 1994. 

Of course this does not mean you cannot have other contract termination points including those included in the promulgated form and any provisions/contingencies (including an inspection contingency) added by a principal. 

I kind of stick to the basic principal the institutional money( hedge funds ) purchased in a and b areas.

You do not care as much about principal pay down as you are substantially increasing the value of the property.

Here it is... 4-plex  Gross Rent $800/per 38400 Less: Vacancy 8% 3072 Gross Potential Rent (GPI)   35328 Expenses     Taxes   5248 Insurance   3600 Principal & Interest   13332 Mgmt.

If you are not planning on holding the departing residence for a minimum of 8-12 years as a rental which still might not be long enough to take a hit to the equity that's there and recover it fully (if it takes such a hit), then sell now and redeploy the equity into your new house (if you are so inclined) or invest it into any number of principle protected low or no load investments that can return at least as much as it will likely earn as equity...with no risk of loss of principal.  

Here are the possible scenarios I'm considering.Pay down the principal on the investment prop.  

Before I invest in any CF platform, I open a direct line of communication (with the principals if possible), do DD on the site and people behind the company and only if I feel 100% comfortable, proceed.