-- emacs startup -- no split screen --

The following code works for me (add into ~/.emacs):

(add-hook 'emacs-startup-hook
    (lambda () (delete-other-windows)) t)

The emacs-startup-hook is run after loading the init file and processing the command line, so all files have been loaded and opened; calling delete-other-windows leaves just one of them visible (normally the last one given on the command line).

Note: you might also need to customize inhibit-startup-screen and set it to t for the above to work.

(setq inhibit-startup-screen t)
(add-hook 'emacs-startup-hook 'delete-other-windows)