20-Lacs biana is too much, 5-Lacs token is sufficient to lock any deal if you can manage the remaining payment in two weeks. Usually, investors do Biana for plots where they get time to arrange the remaining payment in 4-8 weeks. During this time period, investors prefer to sell that plot on higher price and get profit without paying the remaining amount to seller from his pocket. In your case, token is sufficient. You should take receipt of your token properly signed & stamped. Similarly, your dealer will get the token receipt from seller alongwith photocopy of allotment letter to apply NDC. In case if seller is run away during this time period, your dealer will submit that token receipt in DHA office alongwigh photocopy of allotment letter & DHA will declare that plot as Disputed. That means, now that plot can neither be sold or transferred to any other person until he clears his matter with you & you take back your complaint from DHA office.
Even 2-Lacs token is sufficient in ur case.
I hope now u would understand what i try to say