There are several factors you must consider. Decide how you will use the instrument and purchase an instrument for that purpose. Attempting to purchase an instrument for exploring the harpsichord literature, teaching, practicing, and performing may lead you to purchase too much or too little instrument. The size and sound of the instrument will be different accordingly. The Basics Consider the commitments of harpsichord ownership.
Harpsichords require ongoing tuning and maintenance to a much higher degree than many expect.
Changing strings, cutting new plectra and adjusting string dampers are considered routine maintenance. While others can be paid to do these things, cost or availability of technicians may be limiting and expensive. You must also be able to provide a suitable physical environment to ensure the long term health of your instrument. Assess your level of musical expressiveness that you will require in an instrument. Decide how important the degree of which you must be able to match the stylistic nuances are for each musical period.