I sold and made RO Systems for years, one possibility is to rent an ro from Culligan, ecowater or any other large water treatment companies they will rent for about 20-$45.00 per month, production should be around 20-50 gallons per day, though this is dependent on influent temperature and membrane type , and of course tds. The dealer should be able to give you a good idea of what production averages from his units. The dealer normally includes maintenance on the units
Have also seen ro units available from big box retailers ,Sears(expensive), home depot, sams, lowes, these units can sometimes be some really good deals if you are handy with tools and comfortable around plumbing.Look for a TFC membrane, this is the best you can buy but it has some limitations , IT CANNOT BE EXPOSED TO CHLORINE , OR CHLORAMINES which are used to disinfect your water. Chlorine and other oxydizing compounds will tear up a tfc membrane in short order, and since there is no disinfection ,the membrane vessel can be come contaminated with bacterial growth. In a tfc system you must have a SOLID BLOCK CARBON FILTER BEFORE THE MEMBRANE.
Before the solid block you must have a 5 micron string wound or other material filter, do not use paper , these are cheap and usually only good for about a couple of weeks.......To Be Continued