practical approach is to search for them in low-luminosity type 1 active galactic nuclei (AGNs) with mass estimated from their broad-line width and luminosity using empirical virial relationships (e.g., Gebhardt et al. 2000b; Kaspi et al. 2000). This technique has yielded a sample of $\sim 200-300$ candidate BHs with masses between $10^5$ to $10^6$ [$M_{\odot}$]{}(Greene & Ho 2004, 2007b; Dong et al. 2012b), including a couple below $10^5$ [$M_{\odot}$]{}, in the regime of so-called intermediate-mass BHs (IMBH, $10^{3-6}$ [$M_{\odot}$]{}; Filippenko & Ho 2003; Barth et al. 2004; Dong et al. 2007; see reviews in Ho 2008; Kormendy & Ho 2013). The host galaxies of low-mass BHs thus found appear very different from their supermassive counterparts. The best nearby example, NGC 4395, is a dwarf Sdm galaxy without a bulge at all (Filippenko & Ho 2003), while the second prototype, POX 52, is instead a spheroidal or dwarf elliptical galaxy (Barth et al. 2004; Thornton et al. 2008). According to the studies to date, the [$M_\mathrm{BH}$]{}–$\sigma_{\star}$ relation of local inactive massive galaxies appears to roughly extend to the low-mass end (Barth et al. 2005; Greene & Ho 2006; Xiao et al. 2011), but the [$M_\mathrm{BH}$]{}–$L_{\rm bulge}$ relation does not. Photometric decomposition 