Hey Joseph,Congratulations for thinking of starting at your young age.To get a loan, find someone in your network who believe in you: Family, friends, etc. who is willing to act as a guarantor on the loan, if you cannot secure it yourself.You would have to come up with some capital to put down as a down payment.

One of my companies was able to secure a cash LOC without a PG a few weeks ago.

It takes time.Here a few Tips:ADS - Fine-tune your approach and search for the "right" person/partner by placing an ad on a regular basis here on Bigger Pockets.

You could also focus on the great financial advantages of renting/down-sizing (travel more, no more yard to care for/repairs, buy an RV, visit family more)Host a senior-focused event at your facility (maybe show an uncut version of Woodstock haha) or live music, a Social Security expert speaker or Doctor to address health issues, a fund-raiser, art show, etc. and hand out flyers with a special "one month free" coupon attached Have exercise classes for seniorsWeekly bingo nightsPromote your events for free on community calendars, newspapers, seniors sections of papersPrint door hangers and get some kids to hang the door hangers at trailer parks, older communitiesEncourage your current tenants to invite friendsRent a 15-passenger bus ($50) and offer free transportation to key eventsSponsor events at senior centers in the areaCo-Sponsor service club (Rotary, Kiwanis, etc who have many senior members) eventsPut up banners and balloons when you have eventsI hope at least a few of those ideas might spark some interest.

And I would hesitate to use anything other than conventional lending while just getting started and on Active Duty, because small mistakes can ultimately put your security clearance in jeopardy.  

Banks then could see you as a more secure option and give you business line of credit. and you have now executed a viable business plan that banks can see. 

How can I make potential tenants feel at ease when reading listing, to legitimacy of offering so they feel secure in dealing with me, putting deposits, etc.

We've taken the first steps to secure the land. 

I pay interest on the money while it's in use, secure it with a note and deed of trust on the property, and then split the profit's 50/50 or in proportion to the amount of the investment compared to the total cost. 

The idea of doing it prefab vs regular construction came up.Will the building value be affected if prefab?