The wall will take 5 years. Until then Trump would have to use the Romney model which four years ago he described as mean.
Trump building projects have ALWAYS finished AHEAD of schedule and UNDER budget. Stark example is the skating rink in NY city. It was under construction for several years, but not completed. Trump took over, redesigned the rink, tore up the old construction, and finished a new working skating rink in a few months.
History is prologue.