  Galaxy-galaxy lensing (GGL) and clustering measurements from the Dark Energy
Spectroscopic Instrument Year 1 (DESI Y1) dataset promise to yield
unprecedented combined-probe tests of cosmology and the galaxy-halo connection.
In such analyses, it is essential to identify and characterise all relevant
statistical and systematic errors. In this paper, we forecast the covariances
of DESI Y1 GGL+clustering measurements and characterise the systematic bias due
to redshift evolution in the lens samples. Focusing on the projected clustering
and galaxy-galaxy lensing correlations, we compute a Gaussian analytical
covariance, using a suite of N-body and log-normal simulations to characterise
the effect of the survey footprint. Using the DESI One Percent Survey data, we
measure the evolution of galaxy bias parameters for the DESI Luminous Red
Galaxy (LRG) and Bright Galaxy Survey (BGS) samples. We find mild evolution in
the LRGs in 0.4 < z < 0.8, subdominant compared to the expected statistical
errors. For BGS, we find less evolution effects for brighter absolute magnitude
cuts, at the cost of reduced sample size. We find that with a fiducial redshift
bin width delta z = 0.1, evolution effects on GGL is negligible across all
scales, all fiducial selection cuts, all fiducial redshift bins, given DESI Y1
sample size. Galaxy clustering is more sensitive to evolution due to the bias
squared scaling. Nevertheless the redshift evolution effect is insignificant
for clustering above the 1-halo scale of 0.1Mpc/h. For studies that wish to
reliably access smaller scales, additional treatment of redshift evolution is
likely needed. This study serves as a reference for GGL and clustering studies
using the DESI Y1 sample
