I hate to be an arse here but the leyline/hallows plots resolve around following the leylines and seeing what you encounter along the way, which is to say Salem does not know he is going to end up at the flea market until he gets there.
The plots are smaller, more episodic and focus around the many and various supernatural elements a mage might/could encounter while traversing the fallen world. (the site doesn't use arcane experience but I aim for these plots to be reminiscent of scenarios or situations that would grant that RAW).
Knowing he is going to be out and about exploring prep is absolutely a good idea and worthwhile but without invoking a means to divine the future Salem just doesn't have this level of information to work with. After he has been, a follow up glimpse for research and digging into whatever he encounters would be absolutely on the table though!
Also please remember the contagion penalty when casting spells! Salem only has stamina 2 and 4 spells in pattern from rituals. Meaning he has -2 to all spell casting rolls currently (combined spells count as one spell for spell control but each spell still counts separately as normal for spell tolerance)